Question

所以，基本上我需要达到这个效果，有什么建议吗？

JOIN ((CASE WHEN (SELECT COUNT(e.order_id) FROM entry ee WHERE ee.order_id = o.id) > 1
           THEN (SELECT * FROM entry e WHERE e.user_id = 3 )
           ELSE (SELECT * FROM entry e WHERE e.user_id = 3 AND e.draw_id = (SELECT dd.id
                                                      FROM draw dd
                                                      WHERE dd.draw_date_time > CURRENT_TIMESTAMP(0)
                                                      ORDER BY dd.draw_date_time ASC
                                                      LIMIT 1))
           END) e ON e.order_id = o.id

Answer 1

不是你怎么做的。将条件放在on子句中。如果我正确地遵循逻辑：

JOIN
(SELECT e.*, ROW_NUMBER() OVER (PARTITION BY ee.order_id) as cnt
 FROM entry e
) e
ON e.order_id = o.id and
   e.user_id = 3 and 
   (e.cnt <= 1 or
    e.draw_id = (SELECT dd.id
                 FROM draw dd
                 WHERE dd.draw_date_time > CURRENT_TIMESTAMP(0)
                 ORDER BY dd.draw_date_time ASC
                 LIMIT 1
                )

我怀疑这可以进一步简化。如果没有更大的查询的上下文和逻辑应该做什么的解释，很难提出建议。你可能想问另一个问题。

如何在PostgreSQL中使用Case语句？

1 个答案: