How to add composite unique column to mysql table

Question

I have a table:

• user_id int Composite Unique (deal_id + user_id+deal_type) .
• deal_id int
• deal_type varchar .
• created_on datetime .

This is my table. I want to create a composite unique column user_id so that one user can only have a unique deal_id for each deal_type .

How to make composite unique to in mysql phpmyadmin .

Answer 1

 ALTER TABLE my_table ADD UNIQUE KEY (user_id, deal_type, deal_id);