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行失败了......

更新： 表看起来像这样：

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：我有一个相关的，在此处延伸Does row exist and multiple where

Answer 1

您不需要第二个where，第二个and可能是or：

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

（我认为你想要一个or的原因是因为你有一个矛盾的条款meta_key = 'school' AND meta_key = 'hidden'的结合，这总是假的。）

编辑：为了回应OP对他想要获得的结果的评论，这是一个不同的查询：

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')

现在联接条款不再矛盾，因为它们引用了两个不同的行m1和m2。

Answer 2

您不能拥有多个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')

多个Where条件

2 个答案: