多个Where条件

Question

无法正确使用此语法：

SELECT DISTINCT id 
FROM metadata 
WHERE (meta_key = 'school' AND meta_value = 'Some School') 
AND WHERE (meta_key = 'hidden' AND meta_value = '1')

它在第 4 行失败...

更新： 表格如下所示：

meta_id - id - meta_key     - meta_value
1         1    school         Some School 1
2         1    hidden         0
3         2    school         Some School 2
4         2    hidden         1
5         3    school         Some School 3
6         3    hidden         0
7         4    school         Some School 4
8         4    hidden         0
9         5    school         Some School 5
10        5    hidden         1

更新：我在这里有一个相关的扩展行是否存在且存在多个where

Answer 1

您不需要第二个 where，第二个 and 可能旨在成为 or：（

SELECT DISTINCT id 
FROM metadata 
WHERE (meta_key = 'school' AND meta_value = 'Some School') 
OR (meta_key = 'hidden' AND meta_value = '1')

我认为您想要一个 < code>or 是因为否则你会得到一个矛盾子句的连词 meta_key = 'school' AND meta_key = 'hidden'，这总是错误的）。

编辑：为了回应OP关于他试图获得的结果的评论，这里有一个不同的查询：

SELECT DISTINCT m1.id 
FROM metadata m1
join metadata m2 on m1.id = m2.id
WHERE (m1.meta_key = 'school' AND m1.meta_value = 'Some School') 
AND (m2.meta_key = 'hidden' AND m2.meta_value = '1')

现在连词子句不再矛盾，因为它们引用了两个不同的行m1< /code> 和 m2。

Answer 2

不能有多个 WHERE 子句。我想你的意思是

SELECT DISTINCT id 
FROM metadata 
WHERE (meta_key = 'school' AND meta_value = 'Some School') 
    OR (meta_key = 'hidden' AND meta_value = '1')