SQL:我们需要 ANY/SOME 和 ALL 关键字吗? [英] SQL: do we need ANY/SOME and ALL keywords?

问题描述

我使用 SQL(SQL Server、PostgreSQL)超过 10 年，但我从未在我的生产代码中使用过 ANY/SOME 和 ALL 关键字.我遇到的所有情况我都可以通过 IN、MAX、MIN、EXISTS 逃脱，我认为它更具可读性.

I'm using SQL (SQL Server, PostgreSQL) over 10 years and still I'm never used ANY/SOME and ALL keywords in my production code. All situation I've encountered I could get away with IN, MAX, MIN, EXISTS, and I think it's more readable.

例如:

-- = ANY
select * from Users as U where U.ID = ANY(select P.User_ID from Payments as P);

-- IN
select * from Users as U where U.ID IN (select P.User_ID from Payments as P);

或

-- < ANY
select * from Users as U where U.Salary < ANY(select P.Amount from Payments as P);

-- EXISTS
select * from Users as U where EXISTS (select * from Payments as P where P.Amount > U.Salary);

使用ANY/SOME和ALL:

• PostgreSQL
• SQL Server
• MySQL
• SQL FIDDLE 示例

所以问题是:我错过了什么吗?是否存在 ANY/SOME 和 ALL 优于其他解决方案的情况?

So the question is: am I missing something? is there some situation where ANY/SOME and ALL shine over other solutions?

推荐答案

我发现 ANY 和 ALL 在您不只是测试相等或不相等时非常有用.考虑

I find ANY and ALL to be very useful when you're not just testing equality or inequality. Consider

'blah' LIKE ANY (ARRAY['%lah', '%fah', '%dah']);

使用我对此问题的回答.

ANY、ALL 和它们的否定可以极大地简化代码，否则这些代码需要非平凡的子查询或 CTE，而且在我看来它们的使用率明显不足.

ANY, ALL and their negations can greatly simplify code that'd otherwise require non-trivial subqueries or CTEs, and they're significantly under-used in my view.

考虑到 ANY 可用于任何运算符.它对 LIKE 和 ~ 非常方便，但也适用于 tsquery、数组成员测试、hstore 键测试等.

Consider that ANY will work with any operator. It's very handy with LIKE and ~, but will work with tsquery, array membership tests, hstore key tests, and more.

'a => 1, e => 2'::hstore ? ANY (ARRAY['a', 'b', 'c', 'd'])

或:

'a => 1, b => 2'::hstore ? ALL (ARRAY['a', 'b'])

如果没有 ANY 或 ALL，您可能必须将它们表示为子查询或 CTE，通过 VALUES 列表生成聚合一个结果.当然，如果你愿意，你可以这样做，但我会坚持使用 ANY.

Without ANY or ALL you'd probably have to express those as a subquery or CTE over a VALUES list with an aggregate to produce a single result. Sure, you can do that if you want, but I'll stick to ANY.

这里有一个真正的警告:在较旧的 Pg 版本上，如果您正在编写 ANY( SELECT ... )，则几乎可以肯定使用 存在(从...中选择 1 ...).如果您使用的版本中优化器会将 ANY (...) 转换为连接，那么您无需担心.如果有疑问，请检查 EXPLAIN 输出.

There's one real caveat here: On older Pg versions, if you're writing ANY( SELECT ... ), you're almost certainly going to be better off in performance terms with EXISTS (SELECT 1 FROM ... WHERE ...). If you're on a version where the optimizer will turn ANY (...) into a join then you don't need to worry. If in doubt, check EXPLAIN output.

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