Some sort of “different auto-increment indexes” per a primary key values

Question

I have got a table which has an id (primary key with auto increment), uid (key refering to users id for example) and something else which f

Answer 1

SQL Server should allow you to do this. If you can't implement this using a computed column (probably not - there are some restrictions), surely you can implement it in a trigger.

MySQL also would allow you to implement this via triggers.