Question

我有这个查询，目前正在返回两个结果

SELECT h1.*
FROM profile AS h1
  INNER JOIN profile h2
    ON (h1.memid = h2.ph_memid
        AND h1.ph_memid = h2.memid)
WHERE h1.event_id = '5496'

但我试图得到的结果只有1或2 ......条件是329和399必须在两个具有相同事件ID的列中意味着

memid ph_memid 
 329      399
399       329

其中事件id的结果必须相同。这里是1。表模式是在 http://sqlfiddle.com/#!2/9d4f1/1 请帮忙。

Answer 1

这或许你需要ie group by和count（）

SELECT h1.*,count(*) as `tot`
FROM profile AS h1
  INNER JOIN profile h2
    ON (h1.memid = h2.ph_memid
        AND h1.ph_memid = h2.memid)
WHERE h1.event_id = '5496'
group by `h1`.`event_id`

如果你想减少更多，即相对于dt（日期）的数量，你需要添加第二组by

SELECT h1.*,count(*) as `tot`
FROM profile AS h1
  INNER JOIN profile h2
    ON (h1.memid = h2.ph_memid
        AND h1.ph_memid = h2.memid)
WHERE h1.event_id = '5496'
group by `h1`.`event_id` , `h1`.`dt`

Answer 2

元组（329,399）和（399,329）相同，因为它们具有相同的值，即它们的较低值（329）相等并且它们的较高值（399）相等。因此，在较低和较高的值上使用不同的选择来获得一个记录而不是两个：

SELECT DISTINCT least(h1.memid, h1.ph_memid), greatest(h1.memid, h1.ph_memid)
FROM profile h1
INNER JOIN profile h2 ON h1.memid = h2.ph_memid AND h1.ph_memid = h2.memid
WHERE h1.event_id = '5496';

顺便说一下，你不要将h2限制为event_id ='5496'。这是故意的吗？

这是SQL小提琴：http://sqlfiddle.com/#!2/9d4f1/25

编辑：如果它只是计数，你感兴趣，使用COUNT（DISTINCT ...）：

SELECT COUNT(DISTINCT least(h1.memid, h1.ph_memid), greatest(h1.memid, h1.ph_memid))
FROM profile h1
INNER JOIN profile h2 ON h1.memid = h2.ph_memid AND h1.ph_memid = h2.memid
WHERE h1.event_id = '5496';

如何从下面的查询中获取结果的计数？

2 个答案: