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

Question

我有以下查询：

            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

这里的问题是重复的userId被计算了两次。 我想避免它。

我怎样才能实现它？

Answer 1

也许你想要COUNT(DISTINCT) ？

COUNT(DISTINCT tu.userId) AS uCount,