How do I tell the MySQL Optimizer to use the index on a derived table?

Question

Suppose you have a query like this...

SELECT T.TaskID, T.TaskName, TAU.AssignedUsers
FROM `tasks` T
    LEFT OUTER JOIN (
        SELECT TaskID, GROUP_CONCAT(U.F         


        

Answer 1

I'm afraid, it's not possible. You have to create a temporary table or a view to use an index.