Question

I am trying to build a mysql query to list all column a’s that have a duplicate column b from a single table. The trick is I have a timestamp on the rows so i need to essentially identify which is the older of the duplicates so i can delete it. Any help would be appreciated.

Answer 1

Just example – this query return duplicate posts, now you just need to execute delete

id| title     | text_desc          | created 
-------------------------------------------------------
1 | The title | description here   |2012-02-21 10:58:58
2 | The title | description here 1 |2012-02-21 10:58:58
3 | The title | description here 3 |2012-02-21 10:58:58

    select bad_rows.*
     from posts as bad_rows
      inner join (
       select title, MIN(id) as min_id
          from posts
           group by title
             having count(*) > 1
          ) as good_rows on good_rows.title = bad_rows.title
            and good_rows.min_id <> bad_rows.id;

Here is the return rows

id| title     | text_desc          | created 
-------------------------------------------------------
2 | The title | description here 1 |2012-02-21 10:58:58
3 | The title | description here 3 |2012-02-21 10:58:58