diff --git a/tests/RelationFilterTest.php b/tests/RelationFilterTest.php
new file mode 100644
index 0000000..6f0c73d
--- /dev/null
+++ b/tests/RelationFilterTest.php
@@ -0,0 +1,1579 @@
+<?php
+
+namespace ipl\Tests\Orm;
+
+use ipl\Orm\Query;
+use ipl\Sql\Connection;
+use ipl\Sql\Test\Databases;
+use ipl\Stdlib\Filter;
+use ipl\Tests\Orm\Lib\Model\Office;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * This test covers several cases of filter combinations where each represents an equivalence class, which are defined
+ * as follows:
+ *
+ * a) Number of conditions: single
+ *  b) Logical Operators: -, NOT
+ *   f) Comparisons: affirmation, negation
+ * a) Number of conditions: multiple
+ *  b) Logical Operators: AND, OR, NOT(AND), NOT(OR)
+ *   c) Number of relations: single
+ *    d) Columns: same, different
+ *     e) Operators: same
+ *      f) Comparisons: affirmation, negation
+ *     e) Operators: different
+ *   c) Number of relations: multiple
+ *    e) Operators: same, different
+ *     f) Comparisons: affirmation, negation
+ *
+ * The tests rely on a few assumptions which are the same for all of them:
+ * - All filters target a to-many relation
+ * - The ORM only differs between negative and affirmative filters, hence why only equal and unequal filters are used
+ * - Negation comparisons only return results if no such matches are made, instead of including results that have other
+ *   non-matches ("Not any of those" instead of "Any other than those")
+ *
+ *  Every test contains at least one proof of concept using a manually crafted SQL query. (Not necessarily the same way
+ *  the ORM constructs it) Such must not fail. If they do, the dataset has changed. The ORM query must return the same
+ *  results.
+ *
+ * @todo NOT(OR) cases are missing
+ */
+class RelationFilterTest extends TestCase
+{
+    use Databases;
+
+    /**
+     * Search for offices where Donald works
+     *
+     * @equivalenceClass a:single, b:-, f:affirmation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testSingleAffirmativeCondition(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e on e.office_id = office.id'
+            . ' WHERE e.name = ?'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[3]['city'] ?? 'not found');
+        $this->assertSame(4, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::equal('employee.name', 'Donald'));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame(4, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald doesn't work
+     *
+     * @equivalenceClass a:single, b:-, f:negation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testSingleNegativeCondition(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e on e.office_id = office.id AND e.name = ?'
+            . ' WHERE e.id IS NULL'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald']
+        )->fetchAll();
+
+        $this->assertSame('New York', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Cuxhaven', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Sydney', $offices[2]['city'] ?? 'not found');
+        $this->assertSame(3, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::unequal('employee.name', 'Donald'));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('New York', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Cuxhaven', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Sydney', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame(3, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald doesn't work
+     *
+     * @equivalenceClass a:single, b:NOT(AND), f:affirmation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testSingleAffirmativeConditionWithNotOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e on e.office_id = office.id'
+            . ' WHERE NOT (e.name = ?)'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Sydney', $offices[3]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[4]['city'] ?? 'not found');
+        $this->assertSame(5, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::none(
+                Filter::equal('employee.name', 'Donald')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Sydney', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[4]['city'] ?? 'not found', $sql);
+        $this->assertSame(5, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald works
+     *
+     * @equivalenceClass a:single, b:NOT(AND), f:negation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testSingleNegativeConditionWithNotOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e on e.office_id = office.id'
+            . ' WHERE NOT (e.name != ? OR e.name IS NULL)'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[3]['city'] ?? 'not found');
+        $this->assertSame(4, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::none(
+                Filter::unequal('employee.name', 'Donald')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame(4, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where either Donald or Huey works
+     *
+     * @equivalenceClass a:multiple, b:OR, c:single, d:same, e:same, f:affirmation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testOrChainTargetingASingleRelationColumnWithTheSameAffirmativeOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e1 on e1.office_id = office.id AND e1.name = ?'
+            . ' LEFT JOIN employee e2 on e2.office_id = office.id AND e2.name = ?'
+            . ' WHERE e1.id IS NOT NULL OR e2.id IS NOT NULL'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Huey']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Sydney', $offices[3]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[4]['city'] ?? 'not found');
+        $this->assertSame(5, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::any(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::equal('employee.name', 'Huey')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Sydney', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[4]['city'] ?? 'not found', $sql);
+        $this->assertSame(5, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where either Donald or Huey doesn't work
+     *
+     * @equivalenceClass a:multiple, b:OR, c:single, d:same, e:same, f:negation
+     * @dataProvider databases
+     * @todo Finds what {@see testAndChainTargetingASingleRelationColumnWithTheSameNegativeOperator}
+     *       does. The exact opposite. Should they really be equal? They are in monitoring, but there
+     *       the results are the other way round. (What ALL(!=) finds here, cannot be found there)
+     *
+     * @param Connection $db
+     */
+    public function testOrChainTargetingASingleRelationColumnWithTheSameNegativeOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e1 on e1.office_id = office.id AND e1.name = ?'
+            . ' LEFT JOIN employee e2 on e2.office_id = office.id AND e2.name = ?'
+            . ' WHERE e1.id IS NULL OR e2.id IS NULL'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Huey']
+        )->fetchAll();
+
+        $this->assertSame('Amsterdam', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Cuxhaven', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Sydney', $offices[3]['city'] ?? 'not found');
+        $this->assertSame(4, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::any(
+                Filter::unequal('employee.name', 'Donald'),
+                Filter::unequal('employee.name', 'Huey')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('Amsterdam', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Cuxhaven', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Sydney', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame(4, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald works or Huey doesn't
+     *
+     * @equivalenceClass a:multiple, b:OR, c:single, d:same, e:different
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testOrChainTargetingASingleRelationColumnWithDifferentOperators(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e1 on e1.office_id = office.id AND e1.name = ?'
+            . ' LEFT JOIN employee e2 on e2.office_id = office.id AND e2.name = ?'
+            . ' WHERE e1.id IS NOT NULl OR e2.id IS NULL'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Huey']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[3]['city'] ?? 'not found');
+        $this->assertSame('Cuxhaven', $offices[4]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[5]['city'] ?? 'not found');
+        $this->assertSame(6, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::any(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::unequal('employee.name', 'Huey')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame('Cuxhaven', $results[4]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[5]['city'] ?? 'not found', $sql);
+        $this->assertSame(6, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where both Donald and Huey work
+     *
+     * @equivalenceClass a:multiple, b:AND, c:single, d:same, e:same, f:affirmation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testAndChainTargetingASingleRelationColumnWithTheSameAffirmativeOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e1 on e1.office_id = office.id AND e1.name = ?'
+            . ' LEFT JOIN employee e2 on e2.office_id = office.id AND e2.name = ?'
+            . ' WHERE e1.id IS NOT NULL AND e2.id IS NOT NULL'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Huey']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[2]['city'] ?? 'not found');
+        $this->assertSame(3, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::all(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::equal('employee.name', 'Huey')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame(3, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where neither Donald nor Huey work
+     *
+     * @equivalenceClass a:multiple, b:AND, c:single, d:same, e:same, f:negation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testAndChainTargetingASingleRelationColumnWithTheSameNegativeOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e1 on e1.office_id = office.id AND e1.name = ?'
+            . ' LEFT JOIN employee e2 on e2.office_id = office.id AND e2.name = ?'
+            . ' WHERE e1.id IS NULL AND e2.id IS NULL'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Huey']
+        )->fetchAll();
+
+        $this->assertSame('New York', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Cuxhaven', $offices[1]['city'] ?? 'not found');
+        $this->assertSame(2, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::all(
+                Filter::unequal('employee.name', 'Donald'),
+                Filter::unequal('employee.name', 'Huey')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('New York', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Cuxhaven', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame(2, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald works and Huey doesn't
+     *
+     * @equivalenceClass a:multiple, b:AND, c:single, d:same, e:different
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testAndChainTargetingASingleRelationColumnWithDifferentOperators(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e1 on e1.office_id = office.id AND e1.name = ?'
+            . ' LEFT JOIN employee e2 on e2.office_id = office.id AND e2.name = ?'
+            . ' WHERE e1.id IS NOT NULL AND e2.id IS NULL'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Huey']
+        )->fetchAll();
+
+        $this->assertSame('Amsterdam', $offices[0]['city'] ?? 'not found');
+        $this->assertSame(1, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::all(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::unequal('employee.name', 'Huey')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('Amsterdam', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame(1, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where either Donald or Huey doesn't work
+     *
+     * @equivalenceClass a:multiple, b:NOT(AND), c:single, d:same, e:same, f:affirmation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testNotChainTargetingASingleRelationColumnWithTheSameAffirmativeOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e1 on e1.office_id = office.id AND e1.name = ?'
+            . ' LEFT JOIN employee e2 on e2.office_id = office.id AND e2.name = ?'
+            . ' WHERE NOT (e1.id IS NOT NULL AND e2.id IS NOT NULL)'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Huey']
+        )->fetchAll();
+
+        $this->assertSame('Amsterdam', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Cuxhaven', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Sydney', $offices[3]['city'] ?? 'not found');
+        $this->assertSame(4, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::none(Filter::all(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::equal('employee.name', 'Huey')
+            )));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('Amsterdam', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Cuxhaven', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Sydney', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame(4, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald and Huey work
+     *
+     * @equivalenceClass a:multiple, b:NOT(AND), c:single, d:same, e:same, f:negation
+     * @dataProvider databases
+     * @todo Finds the exact opposite of {@see testAndChainTargetingASingleRelationColumnWithTheSameNegativeOperator}.
+     *       No wonder, actually. But monitoring doesn't behave the same way :'(
+     *
+     * @param Connection $db
+     */
+    public function testNotChainTargetingASingleRelationColumnWithTheSameNegativeOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' WHERE office.id IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e on e.office_id = office.id'
+            . '  WHERE e.name = ? OR e.name = ?'
+            . '  GROUP BY office.id'
+            . '  HAVING COUNT(e.id) >= 2'
+            . ' )'
+            . ' ORDER BY office.id',
+            ['Donald', 'Huey']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[2]['city'] ?? 'not found');
+        $this->assertSame(3, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::none(Filter::all(
+                Filter::unequal('employee.name', 'Donald'),
+                Filter::unequal('employee.name', 'Huey')
+            )));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame(3, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where either Donald doesn't work or Huey does
+     *
+     * @equivalenceClass a:multiple, b:NOT(AND), c:single, d:same, e:different
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testNotChainTargetingASingleRelationColumnWithDifferentOperators(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e1 on e1.office_id = office.id AND e1.name = ?'
+            . ' LEFT JOIN employee e2 on e2.office_id = office.id AND e2.name = ?'
+            . ' WHERE NOT (e1.id IS NOT NULL AND e2.id IS NULL)'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Huey']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Cuxhaven', $offices[3]['city'] ?? 'not found');
+        $this->assertSame('Sydney', $offices[4]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[5]['city'] ?? 'not found');
+        $this->assertSame(6, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::none(Filter::all(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::unequal('employee.name', 'Huey')
+            )));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Cuxhaven', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame('Sydney', $results[4]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[5]['city'] ?? 'not found', $sql);
+        $this->assertSame(6, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Huey works but not as manager
+     *
+     * @equivalenceClass a:multiple, b:AND, c:single, d:different, e:different
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testAndChainTargetingASingleRelationButDifferentColumnsWithDifferentOperators(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::all(
+                Filter::equal('employee.name', 'Huey'),
+                Filter::unequal('employee.role', 'Manager')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('Sydney', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame(2, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald works as accountant
+     *
+     * @equivalenceClass a:multiple, b:AND, c:single, d:different, e:same, f:affirmation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testAndChainTargetingASingleRelationButDifferentColumnsWithTheSameAffirmativeOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e ON e.office_id = office.id'
+            . ' WHERE e.name = ? AND e.role = ?'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Accountant']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[1]['city'] ?? 'not found');
+        $this->assertSame(2, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::all(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::equal('employee.role', 'Accountant')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame(2, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald doesn't work as accountant
+     *
+     * @equivalenceClass a:multiple, b:AND, c:single, d:different, e:same, f:negation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testAndChainTargetingASingleRelationButDifferentColumnsWithTheSameNegativeOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' WHERE office.id NOT IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e ON e.office_id = office.id'
+            . '  WHERE e.name = ? AND e.role = ?'
+            . '  GROUP BY office.id'
+            . ' )'
+            . ' ORDER BY office.id',
+            ['Donald', 'Accountant']
+        )->fetchAll();
+
+        $this->assertSame('Amsterdam', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Cuxhaven', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Sydney', $offices[3]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[4]['city'] ?? 'not found');
+        $this->assertSame(5, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::all(
+                Filter::unequal('employee.name', 'Donald'),
+                Filter::unequal('employee.role', 'Accountant')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('Amsterdam', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Cuxhaven', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Sydney', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[4]['city'] ?? 'not found', $sql);
+        $this->assertSame(5, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald works or someone else not as accountant
+     *
+     * @equivalenceClass a:multiple, b:OR, c:single, d:different, e:different
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testOrChainTargetingASingleRelationButDifferentColumnsWithDifferentOperators(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e ON e.office_id = office.id'
+            . ' WHERE e.name = ? OR (e.role != ? OR e.role IS NULL)'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Accountant']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[3]['city'] ?? 'not found');
+        $this->assertSame('Cuxhaven', $offices[4]['city'] ?? 'not found');
+        $this->assertSame('Sydney', $offices[5]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[6]['city'] ?? 'not found');
+        $this->assertSame(7, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::any(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::unequal('employee.role', 'Accountant')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame('Cuxhaven', $results[4]['city'] ?? 'not found', $sql);
+        $this->assertSame('Sydney', $results[5]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[6]['city'] ?? 'not found', $sql);
+        $this->assertSame(7, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where either Donald works or any other assistant
+     *
+     * @equivalenceClass a:multiple, b:OR, c:single, d:different, e:same, f:affirmation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testOrChainTargetingASingleRelationButDifferentColumnsWithTheSameAffirmativeOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e ON e.office_id = office.id'
+            . ' WHERE e.name = ? OR e.role = ?'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Assistant']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Sydney', $offices[3]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[4]['city'] ?? 'not found');
+        $this->assertSame(5, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::any(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::equal('employee.role', 'Assistant')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Sydney', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[4]['city'] ?? 'not found', $sql);
+        $this->assertSame(5, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where either Donald doesn't work or no-one as manager
+     *
+     * @equivalenceClass a:multiple, b:OR, c:single, d:different, e:same, f:negation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testOrChainTargetingASingleRelationButDifferentColumnsWithTheSameNegativeOperator(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' WHERE office.id NOT IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e ON e.office_id = office.id'
+            . '  WHERE e.name = ?'
+            . '  GROUP BY office.id'
+            . ' ) OR office.id NOT IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e ON e.office_id = office.id'
+            . '  WHERE e.role = ?'
+            . '  GROUP BY office.id'
+            . ' )'
+            . ' ORDER BY office.id',
+            ['Donald', 'Manager']
+        )->fetchAll();
+
+        $this->assertSame('Amsterdam', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Cuxhaven', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Sydney', $offices[3]['city'] ?? 'not found');
+        $this->assertSame(4, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::any(
+                Filter::unequal('employee.name', 'Donald'),
+                Filter::unequal('employee.role', 'Manager')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('Amsterdam', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Cuxhaven', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Sydney', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame(4, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where not just Huey works or only as a manager
+     *
+     * @equivalenceClass a:multiple, b:NOT(AND), c:single, d:different, e:different
+     * @dataProvider databases
+     * @todo Finds the exact opposite of {@see testAndChainTargetingASingleRelationButDifferentColumnsWithDifferentOperators}.
+     *       No wonder, actually. But monitoring doesn't behave the same way :'(
+     *
+     * @param Connection $db
+     */
+    public function testNotChainTargetingASingleRelationButDifferentColumnsWithDifferentOperators(Connection $db)
+    {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e ON e.office_id = office.id'
+            . ' WHERE NOT (e.name = ? AND e.role != ?)'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Huey', 'Manager']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[3]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[4]['city'] ?? 'not found');
+        $this->assertSame(5, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::none(Filter::all(
+                Filter::equal('employee.name', 'Huey'),
+                Filter::unequal('employee.role', 'Manager')
+            )));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[4]['city'] ?? 'not found', $sql);
+        $this->assertSame(5, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where not just Donald works or not as manager
+     *
+     * @equivalenceClass a:multiple, b:NOT(AND), c:single, d:different, e:same, f:affirmation
+     * @dataProvider databases
+     * @todo Finds Cuxhaven instead of Baghdad. Not wrong, actually. Why does monitoring behave differently?
+     *
+     * @param Connection $db
+     */
+    public function testNotChainTargetingASingleRelationButDifferentColumnsWithTheSameAffirmativeOperator(
+        Connection $db
+    ) {
+        $this->createOfficesAndEmployees($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e ON e.office_id = office.id'
+            . ' WHERE NOT (e.name = ? AND e.role = ?)'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Manager']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[3]['city'] ?? 'not found');
+        $this->assertSame('Sydney', $offices[4]['city'] ?? 'not found');
+        $this->assertSame('Baghdad', $offices[5]['city'] ?? 'not found');
+        $this->assertSame(6, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::none(Filter::all(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::equal('employee.role', 'Manager')
+            )));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame('Sydney', $results[4]['city'] ?? 'not found', $sql);
+        $this->assertSame('Baghdad', $results[5]['city'] ?? 'not found', $sql);
+        $this->assertSame(6, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where ...
+     *
+     * @equivalenceClass a:multiple, b:NOT(AND), c:single, d:different, e:same, f:negation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testNotChainTargetingASingleRelationButDifferentColumnsWithTheSameNegativeOperator(Connection $db)
+    {
+        $this->markTestIncomplete('This test has not been implemented yet.');
+    }
+
+    /**
+     * Search for offices where Donald works in the accounting department
+     *
+     * @equivalenceClass a:multiple, b:AND, c:multiple, e:same, f:affirmation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testAndChainTargetingMultipleRelationsWithTheSameAffirmativeOperator(Connection $db)
+    {
+        $this->createOfficesEmployeesAndDepartments($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e on e.office_id = office.id'
+            . ' LEFT JOIN department d on e.department_id = d.id'
+            . ' WHERE e.name = ? AND d.name = ?'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Accounting']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Barcelona', $offices[1]['city'] ?? 'not found');
+        $this->assertSame(2, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::all(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::equal('employee.department.name', 'Accounting')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Barcelona', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame(2, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald doesn't work in the accounting department
+     *
+     * @equivalenceClass a:multiple, b:AND, c:multiple, e:same, f:negation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testAndChainTargetingMultipleRelationsWithTheSameNegativeOperator(Connection $db)
+    {
+        $this->createOfficesEmployeesAndDepartments($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' WHERE office.id NOT IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e on e.office_id = office.id'
+            . '  LEFT JOIN department d on e.department_id = d.id'
+            . '  WHERE e.name = ? AND d.name = ?'
+            . '  GROUP BY office.id'
+            . ' )'
+            . ' ORDER BY office.id',
+            ['Donald', 'Accounting']
+        )->fetchAll();
+
+        $this->assertSame('Berlin', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Paris', $offices[3]['city'] ?? 'not found');
+        $this->assertSame(4, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::all(
+                Filter::unequal('employee.name', 'Donald'),
+                Filter::unequal('employee.department.name', 'Accounting')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('Berlin', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Paris', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame(4, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald works but not in the accounting department
+     *
+     * @equivalenceClass a:multiple, b:AND, c:multiple, e:different
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testAndChainTargetingMultipleRelationsWithDifferentOperators(Connection $db)
+    {
+        $this->createOfficesEmployeesAndDepartments($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e on e.office_id = office.id'
+            . ' LEFT JOIN department d on e.department_id = d.id'
+            . ' WHERE e.name = ? AND d.name != ?'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Accounting']
+        )->fetchAll();
+
+        $this->assertSame('Berlin', $offices[0]['city'] ?? 'not found');
+        $this->assertSame(1, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::all(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::unequal('employee.department.name', 'Accounting')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('Berlin', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame(1, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where either Donald works or someone else in the accounting department
+     *
+     * @equivalenceClass a:multiple, b:OR, c:multiple, e:same, f:affirmation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testOrChainTargetingMultipleRelationsWithTheSameAffirmativeOperator(Connection $db)
+    {
+        $this->createOfficesEmployeesAndDepartments($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' LEFT JOIN employee e on e.office_id = office.id'
+            . ' LEFT JOIN department d on e.department_id = d.id'
+            . ' WHERE e.name = ? OR d.name = ?'
+            . ' GROUP BY office.id'
+            . ' ORDER BY office.id',
+            ['Donald', 'Accounting']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Paris', $offices[3]['city'] ?? 'not found');
+        $this->assertSame('Barcelona', $offices[4]['city'] ?? 'not found');
+        $this->assertSame(5, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::any(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::equal('employee.department.name', 'Accounting')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Paris', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame('Barcelona', $results[4]['city'] ?? 'not found', $sql);
+        $this->assertSame(5, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Mickey doesn't work or no-one in the accounting department
+     *
+     * @equivalenceClass a:multiple, b:OR, c:multiple, e:same, f:negation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testOrChainTargetingMultipleRelationsWithTheSameNegativeOperator(Connection $db)
+    {
+        $this->createOfficesEmployeesAndDepartments($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' WHERE office.id NOT IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e on e.office_id = office.id'
+            . '  LEFT JOIN department d on e.department_id = d.id'
+            . '  WHERE e.name = ?'
+            . '  GROUP BY office.id'
+            . ' ) OR office.id NOT IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e on e.office_id = office.id'
+            . '  LEFT JOIN department d on e.department_id = d.id'
+            . '  WHERE d.name = ?'
+            . '  GROUP BY office.id'
+            . ' )'
+            . ' ORDER BY office.id',
+            ['Mickey', 'Accounting']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Barcelona', $offices[3]['city'] ?? 'not found');
+        $this->assertSame(4, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::any(
+                Filter::unequal('employee.name', 'Mickey'),
+                Filter::unequal('employee.department.name', 'Accounting')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Barcelona', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame(4, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where either Donald works or no-one in the accounting department
+     *
+     * @equivalenceClass a:multiple, b:OR, c:multiple, e:different
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testOrChainTargetingMultipleRelationsWithDifferentOperators(Connection $db)
+    {
+        $this->createOfficesEmployeesAndDepartments($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' WHERE office.id IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e on e.office_id = office.id'
+            . '  WHERE e.name = ?'
+            . '  GROUP BY office.id'
+            . ' ) OR office.id NOT IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e on e.office_id = office.id'
+            . '  LEFT JOIN department d on e.department_id = d.id'
+            . '  WHERE d.name = ?'
+            . '  GROUP BY office.id'
+            . ' )'
+            . ' ORDER BY office.id',
+            ['Donald', 'Accounting']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Barcelona', $offices[3]['city'] ?? 'not found');
+        $this->assertSame(4, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::any(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::unequal('employee.department.name', 'Accounting')
+            ));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Barcelona', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame(4, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald doesn't work in the accounting department
+     *
+     * @equivalenceClass a:multiple, b:NOT(AND), c:multiple, e:same, f:affirmation
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testNotChainTargetingMultipleRelationsWithTheSameAffirmativeOperator(Connection $db)
+    {
+        $this->createOfficesEmployeesAndDepartments($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' WHERE office.id NOT IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e on e.office_id = office.id'
+            . '  LEFT JOIN department d on e.department_id = d.id'
+            . '  WHERE e.name = ? AND d.name = ?'
+            . '  GROUP BY office.id'
+            . ' )'
+            . ' ORDER BY office.id',
+            ['Donald', 'Accounting']
+        )->fetchAll();
+
+        $this->assertSame('Berlin', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Paris', $offices[3]['city'] ?? 'not found');
+        $this->assertSame(4, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::none(Filter::all(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::equal('employee.department.name', 'Accounting')
+            )));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('Berlin', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Paris', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame(4, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where no Donald doesn't work not in the accounting department
+     *
+     * Or for your convenience: Where Donald works
+     *
+     * @equivalenceClass a:multiple, b:NOT(AND), c:multiple, e:same, f:negation
+     * @dataProvider databases
+     * @todo Just take a look at the POC and wonder how that would ever be automatically generated.
+     *       Especially if you consider adding another comparison into the mix. This is way too
+     *       complex for the ORM to handle let alone for an ordinary user to understand.
+     *
+     * @param Connection $db
+     */
+    public function testNotChainTargetingMultipleRelationsWithTheSameNegativeOperator(Connection $db)
+    {
+        $this->createOfficesEmployeesAndDepartments($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' WHERE NOT (office.id NOT IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e on e.office_id = office.id'
+            . '  WHERE e.name = ?'
+            . '  GROUP BY office.id'
+            . ' ) AND office.id NOT IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e on e.office_id = office.id'
+            . '  LEFT JOIN department d on e.department_id = d.id'
+            . '  WHERE e.name = ? AND d.name = ?'
+            . '  GROUP BY office.id'
+            . ' ))'
+            . ' ORDER BY office.id',
+            ['Donald', 'Donald', 'Accounting']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Berlin', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('Barcelona', $offices[2]['city'] ?? 'not found');
+        $this->assertSame(3, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::none(Filter::all(
+                Filter::unequal('employee.name', 'Donald'),
+                Filter::unequal('employee.department.name', 'Accounting')
+            )));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Berlin', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('Barcelona', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame(3, count($results), $sql);
+    }
+
+    /**
+     * Search for offices where Donald doesn't work or in the accounting department
+     *
+     * @equivalenceClass a:multiple, b:NOT(AND), c:multiple, e:different
+     * @dataProvider databases
+     *
+     * @param Connection $db
+     */
+    public function testNotChainTargetingMultipleRelationsWithDifferentOperators(Connection $db)
+    {
+        $this->createOfficesEmployeesAndDepartments($db);
+
+        $offices = $db->prepexec(
+            'SELECT office.city FROM office'
+            . ' WHERE office.id NOT IN ('
+            . '  SELECT office.id FROM office'
+            . '  LEFT JOIN employee e on e.office_id = office.id'
+            . '  LEFT JOIN department d on e.department_id = d.id'
+            . '  WHERE e.name = ? AND d.name != ?'
+            . '  GROUP BY office.id'
+            . ' )'
+            . ' ORDER BY office.id',
+            ['Donald', 'Accounting']
+        )->fetchAll();
+
+        $this->assertSame('London', $offices[0]['city'] ?? 'not found');
+        $this->assertSame('Amsterdam', $offices[1]['city'] ?? 'not found');
+        $this->assertSame('New York', $offices[2]['city'] ?? 'not found');
+        $this->assertSame('Paris', $offices[3]['city'] ?? 'not found');
+        $this->assertSame('Barcelona', $offices[4]['city'] ?? 'not found');
+        $this->assertSame(5, count($offices));
+
+        $offices = Office::on($db)
+            ->columns(['office.city'])
+            ->orderBy('office.id')
+            ->filter(Filter::none(Filter::all(
+                Filter::equal('employee.name', 'Donald'),
+                Filter::unequal('employee.department.name', 'Accounting')
+            )));
+        $results = iterator_to_array($offices);
+        $sql = $this->getSql($offices);
+
+        $this->assertSame('London', $results[0]['city'] ?? 'not found', $sql);
+        $this->assertSame('Amsterdam', $results[1]['city'] ?? 'not found', $sql);
+        $this->assertSame('New York', $results[2]['city'] ?? 'not found', $sql);
+        $this->assertSame('Paris', $results[3]['city'] ?? 'not found', $sql);
+        $this->assertSame('Barcelona', $results[4]['city'] ?? 'not found', $sql);
+        $this->assertSame(5, count($results), $sql);
+    }
+
+    /**
+     * Create a definite set of permutations with employees and offices
+     *
+     * Employee | Role         | City
+     * -------- | ------------ | ---------
+     * Donald   | Accountant   | London
+     * Huey     | Manager      | London
+     * Donald   | Salesperson  | Amsterdam
+     * Dewey    | Manager      | New York
+     * Donald   | Accountant   | Berlin
+     * Huey     | Manager      | Berlin
+     * Louie    | Cook         | Berlin
+     * -        | -            | Cuxhaven
+     * Huey     | Assistant    | Sydney
+     * Donald   | Manager      | Baghdad
+     * Huey     | Accountant   | Baghdad
+     *
+     * @param Connection $db
+     */
+    protected function createOfficesAndEmployees(Connection $db)
+    {
+        $db->insert('office', ['id' => 1, 'city' => 'London']); // Two
+        $db->insert('employee', ['id' => 1, 'office_id' => 1, 'name' => 'Donald', 'role' => 'Accountant']);
+        $db->insert('employee', ['id' => 2, 'office_id' => 1, 'name' => 'Huey', 'role' => 'Manager']);
+        $db->insert('office', ['id' => 2, 'city' => 'Amsterdam']); // One of the two
+        $db->insert('employee', ['id' => 3, 'office_id' => 2, 'name' => 'Donald', 'role' => 'Salesperson']);
+        $db->insert('office', ['id' => 3, 'city' => 'New York']); // None of the two
+        $db->insert('employee', ['id' => 4, 'office_id' => 3, 'name' => 'Dewey', 'role' => 'Manager']);
+        $db->insert('office', ['id' => 4, 'city' => 'Berlin']); // The two plus another one
+        $db->insert('employee', ['id' => 5, 'office_id' => 4, 'name' => 'Donald', 'role' => 'Accountant']);
+        $db->insert('employee', ['id' => 6, 'office_id' => 4, 'name' => 'Huey', 'role' => 'Manager']);
+        $db->insert('employee', ['id' => 7, 'office_id' => 4, 'name' => 'Louie', 'role' => 'Cook']);
+        $db->insert('office', ['id' => 5, 'city' => 'Cuxhaven']); // None
+        $db->insert('office', ['id' => 6, 'city' => 'Sydney']); // The other one of the two
+        $db->insert('employee', ['id' => 8, 'office_id' => 6, 'name' => 'Huey', 'role' => 'Assistant']);
+        $db->insert('office', ['id' => 7, 'city' => 'Baghdad']); // The two with switched roles
+        $db->insert('employee', ['id' => 9, 'office_id' => 7, 'name' => 'Donald', 'role' => 'Manager']);
+        $db->insert('employee', ['id' => 10, 'office_id' => 7, 'name' => 'Huey', 'role' => 'Accountant']);
+    }
+
+    /**
+     * Create a definite set of permutations with employees, offices and departments
+     *
+     * Employee | Role         | Department | City
+     * -------- | ------------ | ---------- | ---------
+     * Donald   | Accountant   | Accounting | London
+     * Dewey    | Cook         | Kitchen    | London
+     * Donald   | Salesperson  | Kitchen    | Berlin
+     * Huey     | Assistant    | Accounting | Berlin
+     * Huey     | QA Lead      | Kitchen    | Amsterdam
+     * Mickey   | Manager      | Accounting | New York
+     * Mickey   | Cook         | Kitchen    | Paris
+     * Louie    | Accountant   | Accounting | Paris
+     * Donald   | Accountant   | Accounting | Barcelona
+     *
+     * @param Connection $db
+     */
+    protected function createOfficesEmployeesAndDepartments(Connection $db)
+    {
+        $db->insert('office', ['id' => 1, 'city' => 'London']);
+        $db->insert('office', ['id' => 2, 'city' => 'Berlin']);
+        $db->insert('office', ['id' => 3, 'city' => 'Amsterdam']);
+        $db->insert('office', ['id' => 4, 'city' => 'New York']);
+        $db->insert('office', ['id' => 5, 'city' => 'Paris']);
+        $db->insert('office', ['id' => 6, 'city' => 'Barcelona']);
+        $db->insert('department', ['id' => 1, 'name' => 'Accounting']);
+        $db->insert('department', ['id' => 2, 'name' => 'Kitchen']);
+        $db->insert(
+            'employee',
+            ['id' => 1, 'office_id' => 1, 'department_id' => 1, 'name' => 'Donald', 'role' => 'Accountant']
+        );
+        $db->insert(
+            'employee',
+            ['id' => 2, 'office_id' => 1, 'department_id' => 2, 'name' => 'Dewey', 'role' => 'Cook']
+        );
+        $db->insert(
+            'employee',
+            ['id' => 3, 'office_id' => 2, 'department_id' => 2, 'name' => 'Donald', 'role' => 'Salesperson']
+        );
+        $db->insert(
+            'employee',
+            ['id' => 4, 'office_id' => 2, 'department_id' => 1, 'name' => 'Huey', 'role' => 'Assistant']
+        );
+        $db->insert(
+            'employee',
+            ['id' => 5, 'office_id' => 3, 'department_id' => 2, 'name' => 'Huey', 'role' => 'QA Lead']
+        );
+        $db->insert(
+            'employee',
+            ['id' => 6, 'office_id' => 4, 'department_id' => 1, 'name' => 'Mickey', 'role' => 'Manager']
+        );
+        $db->insert(
+            'employee',
+            ['id' => 7, 'office_id' => 5, 'department_id' => 2, 'name' => 'Mickey', 'role' => 'Cook']
+        );
+        $db->insert(
+            'employee',
+            ['id' => 8, 'office_id' => 5, 'department_id' => 1, 'name' => 'Louie', 'role' => 'Accountant']
+        );
+        $db->insert(
+            'employee',
+            ['id' => 9, 'office_id' => 6, 'department_id' => 1, 'name' => 'Donald', 'role' => 'Accountant']
+        );
+    }
+
+    protected function createSchema(Connection $db, string $driver): void
+    {
+        $db->exec('CREATE TABLE office (id INT PRIMARY KEY, city VARCHAR(255))');
+        $db->exec('CREATE TABLE department (id INT PRIMARY KEY, name VARCHAR(255))');
+        $db->exec(
+            'CREATE TABLE employee (id INT PRIMARY KEY, department_id INT,'
+            . ' office_id INT, name VARCHAR(255), role VARCHAR(255))'
+        );
+    }
+
+    protected function dropSchema(Connection $db, string $driver): void
+    {
+        $db->exec('DROP TABLE IF EXISTS employee');
+        $db->exec('DROP TABLE IF EXISTS department');
+        $db->exec('DROP TABLE IF EXISTS office');
+    }
+
+    /**
+     * Format the given query to SQL
+     *
+     * @param Query $query
+     *
+     * @return string
+     */
+    protected function getSql(Query $query): string
+    {
+        list($sql, $values) = $query->getDb()->getQueryBuilder()->assembleSelect($query->assembleSelect());
+        foreach ($values as $value) {
+            $pos = strpos($sql, '?');
+            if ($pos !== false) {
+                if (is_string($value)) {
+                    $value = "'" . $value . "'";
+                }
+
+                $sql = substr_replace($sql, $value, $pos, 1);
+            }
+        }
+
+        return $sql;
+    }
+}