Remove duplicate rows in MySQL

Question

I have a table with the following fields:

id (Unique)
url (Unique)
title
company
site_id

Now, I need to remove rows having same titl

Answer 1

I have a table which forget to add a primary key in the id row. Though is has auto_increment on the id. But one day, one stuff replay the mysql bin log on the database which insert some duplicate rows.

I remove the duplicate row by

1. select the unique duplicate rows and export them

select T1.* from table_name T1 inner join (select count(*) as c,id from table_name group by id) T2 on T1.id = T2.id where T2.c > 1 group by T1.id;

2. delete the duplicate rows by id

3. insert the row from the exported data.

4. Then add the primary key on id