哪有exists使用方法以?学了很久的sqlserver ,总不不知道 exists 深入含义?请前辈指路!!
哪有exists使用方法以?学了很久的sqlserver   ,总不不知道     exists     深入含义?请前辈指路!!

------解决方案--------------------
帮助里有的：
EXISTS
指定一个子查询，检测行的存在。
这个例子比较了两个语义类似的查询。第一个查询使用 EXISTS 而第二个查询使用 IN。注意两个查询返回相同的信息。

USE pubs
GO
SELECT DISTINCT pub_name
FROM publishers
WHERE EXISTS
(SELECT *
FROM titles
WHERE pub_id = publishers.pub_id
AND type = 'business ')
GO

-- Or, using the IN clause:

USE pubs
GO
SELECT distinct pub_name
FROM publishers
WHERE pub_id IN
(SELECT pub_id
FROM titles
WHERE type = 'business ')
GO

下面是任一查询的结果集：

pub_name
----------------------------------------
Algodata Infosystems
New Moon Books

(2 row(s) affected)

还有其他的看帮助吧
------解决方案--------------------
USE pubs
GO
SELECT DISTINCT pub_name
FROM publishers
WHERE EXISTS
(SELECT *
FROM titles
WHERE pub_id = publishers.pub_id
AND type = 'business ')
GO

-- Or, using the IN clause:

USE pubs
GO
SELECT distinct pub_name
FROM publishers
WHERE pub_id IN
(SELECT pub_id
FROM titles
WHERE type = 'business ')
GO