Question

I want to run the following sql command:

ALTER TABLE `my_table` ADD UNIQUE (
`ref_id` ,
`type`
);

The problem is that some of the data in the table would make this invalid, therefore altering the table fails.

Is there a clever way in MySQL to delete the duplicate rows?

Answer 1

if you don’t care which row gets deleted, use IGNORE:

ALTER IGNORE TABLE `my_table` ADD UNIQUE (
`ref_id` ,
`type`
);