[SQL Tutorial] Tables & Keys

Examples

surrogate key (a primary key with no real world meaning)

natural key (a primary key having a purpose in real world)

foreign key (a mapping from this database to another database)

foreign key defs the relationships between tables

Branch table also defines who's the manage
Scranton Branch's mgr_id = 101 => Michael Scott

supervisor id defs a mapping within a table

composite key (two attributes defing the primary key)

Works_With table uses two foreign keys as the primary key