测试T-SQL中的不等式 [英] Testing for inequality in T-SQL

问题描述

我刚刚在WHERE子句中遇到过这个问题：

I've just come across this in a WHERE clause:

AND NOT (t.id = @id)

与此相比如何：

AND t.id != @id

或者用：

AND t.id <> @id

我自己总是写下后者，但显然别人有不同的想法。一个人会比另一个更好吗？我知道使用<> 或！= 将会破坏我使用索引的希望已经有，但肯定上面的第一种方法会遇到同样的问题吗？

I'd always write the latter myself, but clearly someone else thinks differently. Is one going to perform any better than the other? I know that using <> or != is going to bust any hopes for using an index that I might have had, but surely the first approach above will suffer the same problem?

推荐答案

这3个将会获得相同的执行计划

These 3 will get the same exact execution plan

declare @id varchar(40)
select @id = '172-32-1176'

select * from authors
where au_id <> @id

select * from authors
where au_id != @id

select * from authors
where not (au_id = @id)

当然，它还取决于索引本身的选择性。我总是使用au_id<> @id我自己

It will also depend on the selectivity of the index itself of course. I always use au_id <> @id myself

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