Question

Is there a way to create a unique index across tables in a MySQL database?

By unique, I mean,

                table A ids=1,2,5,7... 

                table B ids=3,4,6,8...

Answer 1

I think, it is not possible by directly creating a constraint. But there are some solutions in order for you to get unique IDs.

One suggestion would be is by using TRIGGER. Create a BEFORE INSERT trigger on both tables which checks the ID for existence during INSERT or UPDATE.

Second, is by creating a third table which contains UNIQUE numbers and the other tables: TableA and TableB will then be reference on the third one.