MySQL - Unique foreign key

Question

I have to make one of the foreign keys unique. The problem is, I am getting the following message from the phpMyAdmin:

The following indexes appear to be equal an         


        

Answer 1

mysql > create unique index index_bar_id on foos(bar_id);
mysql > alter table foos add constraint index_bar_id foreign key (bar_id) references bars (id);

Read more at http://sixarm.com/about/mysql-create-indexes-foreign-keys-constraints.html