Database Schema

users

column name	data type	detail
id	integer	null: false, primary key
username	string	null: false, unique, index
email	string	null: false, unique, index
password_digest	string	null: false
session_token	string	null: true, unique, index
created_at	datetime	null: false
updated_at	datetime	null: false

• has_many include: playlists, likes, liked_songs, liked_playlists, liked_artists, liked_albums

  has_many :liked_songs, 
    through: :likes,
    source: :likeable, 
    source_type: :Song
  
  has many :playlists,
    primary_key: :id,
    foreign_key: :creator_id,
    class_name: :Playlist

genres

column name	data type	detail
id	integer	null: false, primary key
name	string	null: false, unique, index
created_at	datetime	null: false
updated_at	datetime	null: false

• has_many include: artists

artists

column name	data type	detail
id	integer	null: false, primary key
name	string	null: false, unique, index
genre_id	integer	null: false, foreign key
created_at	datetime	null: false
updated_at	datetime	null: false

• has_many include: albums
• belongs_to include: genre

albums

column name	data type	detail
id	integer	null: false, primary key
name	string	null: false, unique, index
year	integer	null: false
artist_id	integer	null: false, index, foreign key
created_at	datetime	null: false
updated_at	datetime	null: false

• has_many include: songs
• belongs_to include: artist

songs

column name	data type	detail
id	integer	null: false, primary key
title	string	null: false, index
album_id	string	null: false, index, foreign key
created_at	datetime	null: false
updated_at	datetime	null: false

• has_many include:
• belongs_to include: album

playlists

column name	data type	detail
id	integer	null: false, primary key
title	string	null: false, unique, index
creator_id	integer	null: false, foreign key
created_at	datetime	null: false
updated_at	datetime	null: false

• has_many include: playlists_songs
• belongs_to include: creator -> user
• has_many :songs, through: :playlists_songs

playlists_songs

column name	data type	detail
id	integer	null: false, primary key
playlist_id	integer	null: false, foreign key
song_id	integer	null: false, foreign_key
created_at	datetime	null: false
updated_at	datetime	null: false

• belongs_to include: playlists, songs

Playlist.find(1).songs

SELECT * FROM songs
  INNER JOIN playlists_songs ON playlists_songs.song_id = songs.id
  where playlists_songs.playlist_id = 1

Likes

column name	data type	detail
id	integer	null: false, primary key
user_id	integer	null: false, foreign key
likeable_id	integer	null: false, foreign_key
likeable_type	string	null: false
created_at	datetime	null: false
updated_at	datetime	null: false

• belongs_to include: user, likeable

• belongs_to :likeable, polymorphic: true