使用 NOT EXISTS 子句编写查询，而没有 NOT EXISTS 的子查询 [英] Writing a query with a NOT EXISTS clause without a subquery for the NOT EXISTS

问题描述

我有兴趣为应用程序编写查询，在该应用程序中我需要使用 NOT EXISTS 子句来检查行是否存在.

I was interested in writing a query for an application where I need to use a NOT EXISTS clause to check if a row exists.

我正在使用 Sybase，但我想知道是否有 SQL 中的一般示例，您可以在其中编写具有 NOT EXISTS 子句的查询，而没有 NOT 的嵌套子查询存在.

I am using Sybase but I would like to know if there is an example in SQL in general where you can write a query having a NOT EXISTS clause without a nested subquery for the NOT EXISTS.

所以代替

SELECT * FROM TABLE 
WHERE NOT EXISTS (SOME SUBQUERY) 

有没有办法在没有子查询的情况下编写这个?

is there a way to write this without a subquery?

编辑:不幸的是，我无法向您展示查询，因为它是机密信息，但我可以解释的是我正在尝试这样做:

EDIT: unfortunately, I cannot show you the query since it is confidential information but what I can explain is that I am trying to do this:

SELECT t1.a 
FROM (select t2.a from table t2 ,table t3 where t2.b = t3.b ) as t1
where not exists (select t1.a from table t1 ) 

希望清楚.

推荐答案

您可以使用 LEFT JOIN 而不是 EXISTS 来编写反联接:

You could write an anti-join using LEFT JOIN instead of an EXISTS:

SELECT t1.*
FROM Table1 t1
LEFT JOIN Table2 t2
    ON  t2.Id = t1.Id
WHERE t2.Id IS NULL

但是对于 EXISTS 操作符，你必须有一个子查询.

But with the EXISTS operator, you must have a subquery.

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