mysql update query with sub query

Question

Can anyone see what is wrong with the below query?

When I run it I get:

#1064 - You have an error in your SQL syntax; check the manual that co

Answer 1

The main issue is that the inner query cannot be related to your where clause on the outer update statement, because the where filter applies first to the table being updated before the inner subquery even executes. The typical way to handle a situation like this is a multi-table update.

Update
  Competition as C
  inner join (
    select CompetitionId, count(*) as NumberOfTeams
    from PicksPoints as p
    where UserCompetitionID is not NULL
    group by CompetitionID
  ) as A on C.CompetitionID = A.CompetitionID
set C.NumberOfTeams = A.NumberOfTeams

Demo: http://www.sqlfiddle.com/#!2/a74f3/1