bloominstituteoftechnology · Mister-Corn · Sep 2, 2018 · Sep 4, 2018
diff --git a/README.md b/README.md
@@ -70,49 +70,143 @@ column names in the following tables. We'll use `setup.sql` later.
   * A reference to an `id` in table `album` (the album the track is on). This
     should be a _foreign key_.
 
+```sql
+CREATE TABLE track(
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  title VARCHAR(128) NOT NULL,
+  album_id INTEGER NOT NULL,
+  FOREIGN KEY(album_id) REFERENCES album(id)
+);
+```
+
 * Create a table called `artist_album` to connect artists to albums. (Note that
   an artist might have several albums and an album might be created by multiple
   artists.)
   * Use foreign keys for this, as well.
 
+ ```sql
+ CREATE TABLE artist_album(
+   id INTEGER PRIMARY KEY AUTOINCREMENT,
+   artist_id INTEGER NOT NULL,
+   album_id INTEGER NOT NULL,
+   FOREIGN KEY(artist_id) REFERENCES artist(id),
+   FOREIGN KEY(album_id) REFERENCES album(id)
+ );
+ ```
+
 * Run the queries in the file `setup.sql`. This will populate the tables.
   * Fix any errors at this point by making sure your tables are correct.
   * `DROP TABLE` can be used to delete a table so you can recreate it with
     `CREATE TABLE`.
 
 * Write SQL `SELECT` queries that:
   * Show all albums.
+  ```sql
+  SELECT * FROM album;
+  ```
   * Show all albums made between 1975 and 1990.
+  ```sql
+  SELECT * FROM album WHERE release_year BETWEEN 1975 AND 1990;
+  ```
   * Show all albums whose names start with `Super D`.
+  ```sql
+  SELECT * FROM album WHERE title LIKE 'Super D%';
+  ```
   * Show all albums that have no release year.
+  ```sql
+  SELECT * FROM album WHERE release_year IS NULL;
+  ```
+
+---
+
+Great resources: 
+* [sqlite-select](http://www.sqlitetutorial.net/sqlite-select/) 
+* [sqlite-where](http://www.sqlitetutorial.net/sqlite-where/)
+* [where-isnull](https://www.dofactory.com/sql/where-isnull)
+* [sqlite-avg](http://www.sqlitetutorial.net/sqlite-avg/)
+* [formatting sqlite shell output](https://dba.stackexchange.com/a/40672)
+
+---
 
 * Write SQL `SELECT` queries that:
   * Show all track titles from `Super Funky Album`.
+  ```sql
+  SELECT track.title 
+    FROM track 
+    JOIN album ON album.id = track.album_id 
+    WHERE album.title IS 'Super Funky Album';
+  ``` 
   * Same query as above, but rename the column from `title` to `Track_Title` in
     the output.
-
+  ```sql
+  SELECT track.title AS Track_Title 
+    FROM track 
+    JOIN album ON album.id = track.album_id 
+    WHERE album.title IS 'Super Funky Album';
+  ``` 
   * Select all album titles by `Han Solo`.
-
+  ```sql
+  SELECT artist.name AS Artist, album.title AS Album_Title 
+    FROM album 
+    JOIN artist_album ON artist_album.album_id = album.id 
+    JOIN artist ON artist.id = artist_album.artist_id 
+    WHERE artist.name IS 'Han Solo';
+  ```
   * Select the average year all albums were released.
+  ```sql
+  SELECT avg(release_year) FROM album;
+  ```
 
   * Select the average year all albums by `Leia and the Ewoks` were released.
+  ```sql
+  SELECT AVG(release_year)
+    FROM album
+    JOIN artist_album ON artist_album.album_id = album.id 
+    JOIN artist ON artist.id = artist_album.artist_id 
+    WHERE artist.name IS 'Leia and the Ewoks';
+  ```
 
   * Select the number of artists.
+  ```sql
+  SELECT COUNT(*) AS Number_of_Artists FROM artist;
+  ```
 
   * Select the number of tracks on `Super Dubstep Album`.
+  ```sql
+  SELECT COUNT(*) AS Number_of_Tracks
+    FROM track
+    JOIN album ON album.id = track.album_id
+    WHERE album.title IS 'Super Dubstep Album';
+  ```
 
 ### Exercises, Day 2
 
 Create a database for taking notes.
 
 * What are the columns that a note table needs?
 
+|Columns      |Relation |
+|:---:        |:---:    |
+|id           |Primary  |
+|title        |         |
+|note_text    |         |
+|date_created |         |
+|author_id    |Foreign  |
+
 * If you have a timestamp field, how do you auto-populate it with the date?
 
+Per this [StackOverflow answer](https://stackoverflow.com/a/14462319), use `CURRENT_TIMESTAMP` 
+as the default value.
+
 * A note should have a foreign key pointing to an author in an author table.
 
 * What columns are needed for the author table?
 
+|Columns      |Relation |
+|:---:        |:---:    |
+|id           |Primary  |
+|author_name  |         |
+
 Write queries that:
 
 * Insert authors to the author table.
@@ -129,9 +223,13 @@ Write queries that:
   > Note that SQLite doesn't enforce foreign key constrains by default. You have
   > to enable them by running `PRAGMA foreign_keys = ON;` before your queries.
 
-  * What happens when you try to delete an author with an existing note?
-  * How can you prevent this?
+  * What happens when you try to delete an author with an existing note?<br/>
+  `FOREIGN KEY constraint failed`<br/>
+  This happens because we are trying to authors, but will end up leaving notes with foreign keys pointing to nowhere if we do so, so the deletion is stopped.
 
+  * How can you prevent this?
+  We can set `ON DELETE CASCADE`, which will delete all related rows with a foreign key matching the author being deleted.
+
 Submit a file `notes.sql` with the queries that build (`CREATE TABLE`/`INSERT`)
 and query the database as noted above.
 
diff --git a/music.db b/music.db
diff --git a/notes.db b/notes.db
diff --git a/notes.sql b/notes.sql
@@ -0,0 +1,66 @@
+CREATE TABLE note(
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  title VARCHAR(128) DEFAULT 'New Note',
+  note_text TEXT,
+  author_id INTEGER NOT NULL,
+  date_created DATETIME DEFAULT CURRENT_DATE,
+  FOREIGN KEY(author_id) REFERENCES author(id) ON DELETE CASCADE
+);
+
+CREATE TABLE author(
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  author_name VARCHAR(64) NOT NULL
+);
+
+INSERT INTO author (id, author_name) VALUES (1, "Alfa");
+INSERT INTO author (id, author_name) VALUES (2, "Bravo");
+INSERT INTO author (id, author_name) VALUES (3, "Charlie");
+
+INSERT INTO note (id, title, note_text, author_id) VALUES (
+  1,
+  'My friend Omega',
+  'My friend, Omega, is the last word when it comes to friendship',
+  1
+);
+
+INSERT INTO note (id, title, note_text, author_id) VALUES (
+  2,
+  'Lorem Ipsum',
+  'Cras aliquam, diam ut pretium ultrices, quam lectus pretium nulla, at molestie lacus nisl sed eros. Aliquam vitae lacus quis quam eleifend mattis. Mauris tempor pulvinar facilisis.',
+  1
+);
+
+INSERT INTO note (id, title, note_text, author_id) VALUES (
+  3,
+  'My favorite television channel',
+  'My favorite television channel on cable is Lifetime. It is the best.',
+  2
+);
+
+INSERT INTO note (id, title, note_text, author_id) VALUES (
+  4,
+  'Dissertation on Chocolate Factories',
+  'Access to the means of chocolate production should not be reserved for the golden-tickted elite, but for the hungry and impoverished masses!',
+  3
+);
+
+.headers ON
+.mode column
+
+SELECT *
+  FROM note
+  JOIN author ON author.id = note.author_id;
+
+SELECT *
+  FROM note
+  WHERE note.id = 4;
+
+SELECT author.author_name, COUNT(note.title) AS Num_of_Notes
+  FROM note
+  JOIN author ON author.id = note.author_id
+  GROUP BY author.author_name;
+
+PRAGMA foreign_keys = ON;
+
+DELETE
+  FROM author;