how to add composite unique to a column in the table mysql

Question

I have a table:

1. user_id int Composite Unique (deal_id + user_id+deal_type).
2. deal_id int
3. deal_type varchar.
4. created_on datetime.

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

How to make composite unique for in mysql phpmyadmin.

Answer 1

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