Select: Add support for locking clauses

src/QueryBuilder.php

@@ -156,7 +156,8 @@ public function assembleSelect(Select $select, array &$values = [])
             $this->buildGroupBy($select->getGroupBy(), $values),
             $this->buildHaving($select->getHaving(), $values),
             $this->buildOrderBy($select->getOrderBy(), $values),
-            $this->buildLimitOffset($select->getLimit(), $select->getOffset())
+            $this->buildLimitOffset($select->getLimit(), $select->getOffset()),
+            $this->buildFor($select->getFor())
         ]);
 
         $sql = implode($this->separator, $sql);
@@ -684,6 +685,24 @@ public function buildLimitOffset($limit = null, $offset = null)
         return implode($this->separator, $sql);
     }
 
+    /**
+     * Build the locking clause of a query
+     *
+     * @param ?string $lockStrength
+     *
+     * @return string
+     */
+    public function buildFor($lockStrength)
+    {
+        $sql = [];
+
+        if (! empty($lockStrength)) {
+            $sql[] = "FOR $lockStrength";
+        }
+
+        return implode($this->separator, $sql);
+    }
+
     /**
      * Build the UNION parts of a query
      *

src/Select.php

@@ -39,6 +39,9 @@ class Select implements CommonTableExpressionInterface, LimitOffsetInterface, Or
     /** @var array|null Internal representation for the HAVING part of the query */
     protected $having;
 
+    /** @var string The lock strength applied by the query */
+    protected $lockStrength;
+
     /**
      * The queries to UNION
      *
@@ -352,6 +355,30 @@ public function orNotHaving($condition, $operator = Sql::ALL)
         return $this;
     }
 
+    /**
+     * Get the lock strength applied by the query
+     *
+     * @return string
+     */
+    public function getFor()
+    {
+        return $this->lockStrength;
+    }
+
+    /**
+     * Set a lock strength to be applied by the query
+     *
+     * @param string $lockStrength
+     *
+     * @return self
+     */
+    public function for($lockStrength)
+    {
+        $this->lockStrength = $lockStrength;
+
+        return $this;
+    }
+
     /**
      * Get the UNION parts of the query
      *

tests/SelectTest.php

@@ -600,6 +600,17 @@ public function testOffsetWithoutLimit()
         );
     }
 
+    public function testFor()
+    {
+        $this->setupTest();
+
+        $this->query->from('b')->columns('a')->for('UPDATE');
+        $this->assertCorrectStatementAndValues(
+            'SELECT a FROM b FOR UPDATE',
+            []
+        );
+    }
+
     public function testUnion()
     {
         $this->setupTest();