SQL to delete the duplicates in a table

Question

I have a table transaction which has duplicates. i want to keep the record that had minimum id and delete all the duplicates based on four fields DATE, AMOUNT, REFNUMBER, PA

Answer 1

It would probably be more efficient to do something like

DELETE FROM transaction t1
 WHERE EXISTS( SELECT 1
                 FROM transaction t2
                WHERE t1.date = t2.date
                  AND t1.refnumber = t2.refnumber
                  AND t1.parentFolderId = t2.parentFolderId
                  AND t2.id > t1.id )