mysql - How to select complex data from a table and delete it from the same table -

i have feedback table contains user feedbacks , ratings per entity. there cases in multiple users have voted on same entity not desirable , have entered system due glitch.

the table schema this:

qa_id,int(10) //id of entity score,smallint(1) user_id,int(3) feed_time,datetime 

i trying delete 1 of duplicate entries (fortunately there 1 feedback) query:

delete feedback md5(qa_id+feed_time) in  (     select md5(qa_id+feed_time)from feedback fb     group fb.qa_id     having count(fb.qa_id) > 1     order fb.qa_id     desc ) 

it fails saying:

error code : 1093 can't specify target table 'feedback' update in clause (0 ms taken) 

that cannot select , delete same table (i.e. if appears in sub-query). don't have expertise in databases , not allowed use programming language same. :(

any suggestions on how can queries only?

the easiest way fix in mysql put subquery in additional layer of subquery:

delete feedback md5(qa_id+feed_time) in (select *                                (select md5(qa_id+feed_time)                                      feedback fb                                      group fb.qa_id                                      having count(fb.qa_id) > 1                                     ) t                               )