Question

时需要空结果

SELECT * FROM prods 
WHERE prod_id = 3 and (fet_id = 1 and fet_id = 5)

但该代码(fet_id = 1 and fet_id = 5)或(fet_id = 1 and fet_id = 3)不起作用 "Where in"是最好的方法，但是我需要`WHERE IN（1 and 2 and 3）

默认情况下，"WHERE IN"以(1 or 2 or 3)的身份工作

当我选择fet_id = 1和fet_id = 3时，我需要两个结果当我选择fet_id = 1和fet_id = 5时我不需要结果

Answer 1

您可能想要

SELECT prod_id FROM prods GROUP by prod_id
HAVING (SUM(fet_id=1)>0
AND SUM(fet_id=5)>0)
OR 
(SUM(fet_id=1)>0
AND SUM(fet_id=3)>0)

HAVING过滤器将WHERE过滤器组分组。

Answer 2

尝试一下：

SELECT p1.id AS id1, p2.id AS id2
FROM `prods` p1 LEFT JOIN `prods` p2 ON p1.`prod_id` =  p2.`prod_id`
WHERE p1.`fet_id` = '1' AND p2.`fet_id` = '3'

输出

  id1   id2
  1      3

输入fet_id = 1和fet_id = 5

SELECT p1.id AS id1, p2.id AS id2
FROM `prods` p1 LEFT JOIN `prods` p2 ON p1.`prod_id` =  p2.`prod_id`
WHERE p1.`fet_id` = '1' AND p2.`fet_id` = '5'

输出：没有结果

Answer 3

如果需要两个以上的值，则另外一个

SELECT res.* FROM (SELECT 3 as total,
(SELECT COUNT(*) FROM `prods` as t1 WHERE t1.`fet_id` = 1 OR  t1.`fet_id` = 2 OR t1.`fet_id` = 5) as current,
t2.*
FROM `prods` as t2 WHERE t2.`fet_id` in (1,2,5)) as res WHERE res.total = res.current

如何使用和条件选择一些值？

3 个答案: