Creating UNIQUE constraint on multiple columns in MySQL Workbench EER diagram

In the Alter Table dialog of MySQL Workbench:

• Go to Indexes tab.
• Double-click on a blank row to create a new index.
• Choose 'UNIQUE' as the index type.
• Check the columns that you want to be unique together.

There's some discussion as to whether this is weird, since an index is not the same as a constraint. I certainly wouldn't have thought to look there. However, apparently the `unique index' enforces uniqueness in the same way as a unique constraint, and may improve performance. For example, if I try to insert a row that would break unique together after using this method, it throws an '1062 Duplicate entry' error.

it does not seem to be available : http://bugs.mysql.com/bug.php?id=48468 . it seems what you can is to create a multi column unique index on the indexes tab but for a multi column unique constraint, you need to run the creation command manually.