Remove Primary Key in MySQL
ALTER TABLE to add a composite primary key
Is there a REAL performance difference between INT and VARCHAR primary keys?
Unable to update the EntitySet - because it has a DefiningQuery and no <UpdateFunction> element exist
How to 'insert if not exists' in MySQL?
Difference between Key, Primary Key, Unique Key and Index in MySQL
Can I have multiple primary keys in a single table?
How to reset postgres' primary key sequence when it falls out of sync?