sql - If...ELSE with subquery in MySQL -

sql - If...ELSE with subquery in MySQL -

in table 'chat':

i delete messages if have been deleted both sender recipient. if, however, user first delete message, should recorded under "deleted_by" user id (until sec user deletes message).

for message #3 , user #1 query so:

if (select deleted_by chat id=3) <> '1' , (select deleted_by chat id=3) <> '0' delete chat id=3 else update chat set deleted_by=1 id=3 end if

this should delete message #3, instead error. can help me create according sqlfiddle work?

thank you!

a subquery isn't needed. instead, can delete row if other user has marked deleted , if still exists, mark deleted:

delete chat id = 3 , deleted_by <> 0; update chat set deleted_by = 4 id = 3;

mysql sql if-statement subquery