Edward Gonzalez

README.md

@@ -135,3 +135,4 @@ Write queries that:
 Submit a file `notes.sql` with the queries that build (`CREATE TABLE`/`INSERT`)
 and query the database as noted above.
 
+#Initial Commit 

ex1.sql

@@ -0,0 +1,73 @@
+CREATE TABLE album (id INTEGER PRIMARY KEY AUTOINCREMENT, title VARCHAR(128) NOT NULL, release_year INTEGER);
+CREATE TABLE artist (id INTEGER PRIMARY KEY AUTOINCREMENT, name VARCHAR(128) NOT NULL);
+
+/* Exercises, Day 1 */ 
+
+/* 1. Create a table called track that holds information about a music track. It should contain: */ 
+
+	/* - An autoincrementing id */ 
+	/*  A title (of type varchar, probably) */ 
+	/* A reference to an id in table album (the album the track is on). This should be a foreign key. */ 
+
+    CREATE TABLE track (id INTEGER PRIMARY KEY AUTOINCREMENT, title VARCHAR(128) NOT NULL, album_id INTEGER NOT NULL REFERENCES album(id));
+
+/* 2. 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. */ 
+
+    CREATE TABLE artist_album (artist_id INTEGER NOT NULL REFERENCES artist(id), album_id INTEGER NOT NULL REFERENCES album(id));
+
+/* 3. 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. */ 
+
+/* 4. Write SQL SELECT queries that: */ 
+
+	/* - Show all albums. */ 
+
+    SELECT * FROM album;
+
+    /* - Show all albums made between 1975 and 1990. */ 
+
+    SELECT * FROM album WHERE release_year >= 1975 AND release_year <= 1990;    
+
+    /* - Show all albums whose names start with Super D. */ 
+
+    SELECT * FROM album WHERE title LIKE 'Super D%'; 
+
+    /* - Show all albums that have no release year. */ 
+
+    SELECT * FROM album WHERE release_year is NULL;
+
+/* 5. Write SQL SELECT queries that: */ 
+
+	/* - Show all track titles FROM Super Funky Album. */ 
+
+    SELECT title FROM track WHERE title LIKE 'Super Funky%';
+
+	/* - Same query as above, but rename the column FROM title to Track_Title in the output. */ 
+
+    SELECT title AS Track_Title FROM track WHERE title LIKE 'Super Funky%';
+
+    /* - Select all album titles by Han Solo. */ 
+
+    SELECT title FROM (SELECT album.title, artist.name FROM album, artist, artist_album WHERE album.id = artist_album.album_id AND artist.id = artist_album.artist_id) 
+        WHERE name = 'Han Solo';
+
+    /* - Select the average year all albums were released. */ 
+
+    SELECT AVG(release_year) FROM album;
+
+	/* - Select the average year all albums by Leia AND the Ewoks were released. */ 
+
+    SELECT AVG(release_year) FROM (SELECT album.title, album.release_year, artist.name FROM album, artist, artist_album WHERE album.id = artist_album.album_id AND artist.id = artist_album.artist_id) 
+        WHERE name = 'Leia AND the Ewoks';
+
+	/* - Select the number of artists. */ 
+
+    SELECT Count(id) FROM artist;
+
+	/* - Select the number of tracks on Super Dubstep Album. */ 
+
+    SELECT Count(id) FROM track WHERE title LIKE 'Super Dubstep%';

notes.sql

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+/* Create authors table */ 
+
+CREATE TABLE authors (id INTEGER PRIMARY Key AUTOINCREMENT, first_name VARCHAR(200) NOT NULL, last_name VARCHAR(255) NOT NULL);
+
+/* Create notes table */ 
+
+CREATE TABLE notes (id INTEGER PRIMARY Key AUTOINCREMENT, title VARCHAR(200) NOT NULL, content VARCHAR(255) NOT NULL, author_id INTEGER REFERENCES authors(id), created_at DATETIME DEFAULT CURRENT_TIMESTAMP, last_modified DATETIME DEFAULT CURRENT_TIMESTAMP);
+
+/* Create a trigger to update the timestamp for the last_modified field in a record when changes are made to it */ 
+
+CREATE TRIGGER UPDATE_TIMESTAMP_TRIGGER
+AFTER UPDATE ON notes
+BEGIN
+   UPDATE notes SET TIMESTAMP = STRFTIME('%Y-%m-%d %H:%M:%f', 'NOW') WHERE id = NEW.id;
+END;
+
+/* Insert authors to the authors table. */ 
+
+InSERT INTO authors (first_name, last_name) VALUES ('Edward', 'Gonzalez');
+InSERT INTO authors (first_name, last_name) VALUES ('Bob', 'Dillan');
+InSERT INTO authors (first_name, last_name) VALUES ('Maria', 'Stratus');
+InSERT INTO authors (first_name, last_name) VALUES ('Tom', 'Smith');
+
+/* Insert notes to the note table. */ 
+
+InSERT INTO notes (title, content, authors_id) VALUES ('Title 1', 'Content 1', 5);
+InSERT INTO notes (title, content, authors_id) VALUES ('Title 2', 'Content 2', 4);
+InSERT INTO notes (title, content, authors_id) VALUES ('Title 3', 'Content 3', 2);
+InSERT INTO notes (title, content, authors_id) VALUES ('Title 4', 'Content 4', 1);
+InSERT INTO notes (title, content, authors_id) VALUES ('Title 5', 'Content 5', 1);
+
+/*  Select all notes by an author's name. */ 
+
+SELECT title, content FROM notes, authors WHERE authors.id = notes.authors_id AND authors.first_name = 'Edward';
+
+/* Select author for a particular note by note ID. */ 
+
+SELECT first_name, last_name FROM (SELECT notes.id as notes_id, authors.first_name, authors.last_name FROM authors, notes WHERE notes.authors_id = authors.id) WHERE notes_id = 3;
+
+/* Select the names of all the authors along with the number of notes they each have. (Hint: GROUP BY.) */ 
+
+SELECT count(notes_id) notes, first_name, last_name FROM (SELECT notes.id AS notes_id, authors.first_name, authors.last_name FROM authors, notes WHERE notes.authors_id = authors.id) group by first_name, last_name;
+
+/* Delete authors from the author table.(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.) */ 
+
+DELETE FROM authors WHERE id = 4;
+
+/* What happens when you try to delete an author with an existing note? */ 
+
+/* The author id  4 will still be referenced in the notes table. */ 
+
+/* How can you prevent this? */ 
+
+PRAGMA foreign_keys = ON;
+
+/* Since PRAGMA foreign_keys is on you will receive a an error such as "Error: FOREIGN Key constraint failed" when trying to delete an author that is referenced in the notes table. */