SQL逻辑运算符优先级:And and Or
下面的两个语句是否等效?SELECT [...]
FROM [...]
WHERE some_col in (1,2,3,4,5) AND some_other_expr
和
SELECT [...]
FROM [...]
WHERE some_col in (1,2,3) or some_col in (4,5) AND some_other_expr
我可以使用某种真值表来验证这一点吗?
解决方案:
And优先于Or,因此,即使aa1 Or a2
Where a And b
与…不同
Where a1 Or a2 And b,
因为那将被执行为
Where a1 Or (a2 And b)
并且想要使它们相同,是以下内容(使用括号覆盖优先级规则):
Where (a1 Or a2) And b
这是一个示例说明:
Declare @x tinyInt = 1
Declare @y tinyInt = 0
Declare @z tinyInt = 0
Select Case When @x=1 OR @y=1 And @z=1 Then 'T' Else 'F' End -- outputs T
Select Case When (@x=1 OR @y=1) And @z=1 Then 'T' Else 'F' End -- outputs F
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