Creating tables with multiple primary keys

[Guest_imported]

I tried to create tables with more than one primary keys, but I got the "multiple primary keys devined" error messages. Could anyone tell me how to do that in MySQL? Thanks!

 

[petersJazz]

Its in the principle of relation databases that there can be just one primary key. But on the other hand, a primary key is just another unique index.

So, if you like to have two "primary keys" on a table you create one primary key and a unique key.

create table xxx (
id1 int not null,
id2 int not null,
...
primary key (id1));

create unique index xxx_ix on xxx(id2);