Question

I have a table taged with two fields sesskey (varchar32 , index) and products (int11), now I have to delete all rows that having group by sesskey count(*) = 1.
I’m trying a fews methods but all fails.

Example:

delete from taged where sesskey in (select sesskey from taged group by sesskey having count(*) = 1)

The sesskey field could not be a primary key because its repeated.

Answer 1

DELETE  si
FROM    t_session si
JOIN    (
        SELECT  sesskey
        FROM    t_session so
        GROUP BY
                sesskey
        HAVING  COUNT(*) = 1
        ) q
ON      q.sesskey = si.sesskey

You need to have a join here. Using a correlated subquery won’t work.

See this article in my blog for more detail:

• Keeping rows