== Релации: ==
= Track =
 * __**track_id**__ (PK)
 * **name** (NOT NULL)
 * album_id* (FK → Album)
 * media_type_id* (FK → MediaType)
 * genre_id* (FK → Genre)
 * composer
 * **milliseconds** (NOT NULL)
 * **bytes** (NOT NULL)

= Album =
 * __**album_id**__ (PK)
 * **title** (NOT NULL)
 * artist_id* (FK → Artist)

= Artist =
 * __**artist_id**__ (PK)
 * **name** (NOT NULL)

= Genre =
 * __**genre_id**__ (PK)
 * **name** (NOT NULL)

= MediaType =
 * __**media_type_id**__ (PK)
 * **name** (NOT NULL)

= Price =
 * __**price_id**__ (PK)
 * **value** (NOT NULL)
 * **date** (NOT NULL)
 * track_id* (FK → Track)

= !InvoiceLine =
 * __**invoice_line_id**__ (PK)
 * invoice_id* (FK → Invoice)
 * track_id* (FK → Track)
 * **quantity** (NOT NULL)

= Invoice =
 * __**invoice_id**__ (PK)
 * customer_id* (FK → Customer)
 * **invoice_date** (NOT NULL)
 * billing_address
 * billing_city
 * billing_state
 * billing_country
 * billing_postal_code
 * **total** (NOT NULL)

= Customer =
 * __**customer_id**__ (PK)
 * **first_name** (NOT NULL)
 * **last_name** (NOT NULL)
 * company
 * support_rep_id* (FK → Employee)
 * personal_info_id* (FK → AddressInfo)
 * contact_id* (FK → Contact)

= Employee =
 * __**employee_id**__ (PK)
 * **first_name** (NOT NULL)
 * **last_name** (NOT NULL)
 * **title** (NOT NULL)
 * reports_to* (FK → Employee)
 * **birth_date** (NOT NULL)
 * **hire_date** (NOT NULL)
 * personal_info_id* (FK → AddressInfo)
 * contact_id* (FK → Contact)

= !AddressInfo =
 * __**address_info_id**__ (PK)
 * **address** (NOT NULL)
 * **city** (NOT NULL)
 * state
 * **country** (NOT NULL)
 * **postal_code** (NOT NULL)

= Contact =
 * __**contact_id**__ (PK)
 * **phone** (NOT NULL)
 * fax
 * **email** (NOT NULL)

= Playlist =
 * __**playlist_id**__ (PK)
 * **name** (NOT NULL)

= !PlaylistTrack =
 * __**playlist_track_id**__ (PK)
 * playlist_id* (FK → Playlist)
 * track_id* (FK → Track)