如何避免 SUM 重复（CASE WHEN..THEN 1 ELSE 0 END）？

Question

I ghave following query:

            SELECT col.myId,
                   SUM( CASE WHEN tu.userId IS NOT NULL THEN 1  ELSE 0 END) AS uCount,
                   SUM( CASE WHEN g.grouptype != 12 THEN 1  ELSE 0 END) AS gCount
            FROM myUserTable col
                     LEFT JOIN fooTable elem ON col.myId = elem.myId
                     LEFT JOIN barTable esc ON elem.anotherId = esc.anotherId
                     LEFT JOIN userTable tu ON esc.anotherId = tu.anotherId
                     LEFT JOIN grouTable g ON g.groupid = tu.groupid
            GROUP BY col.myId

The problem here that duplicated userId is counted twice. I want to avoid it.

How can I achieve it?

Answer 1

Perhaps you want COUNT(DISTINCT) ?

COUNT(DISTINCT tu.userId) AS uCount,