如何在IF EXISTS子查询中使用SQL Select语句？
如何在IF EXISTS子查询中使用SQL Select语句？
提问于 2011-10-18 17:20:52
如何使用IF EXISTS语句从子查询中选择布尔值(SQL Server)？
它应该是这样的：
SELECT
TABEL1.Id,
NewFiled = (IF EXISTS(SELECT Id FROM TABLE2 WHERE TABLE2.ID = TABEL1.ID)
SELECT 'TRUE'
ELSE
SELECT 'FALSE')
FROM TABEL1回答 3
Stack Overflow用户
发布于 2011-10-18 17:26:46
也可以使用ISNULL和select语句来获得此结果
SELECT
Table1.ID,
ISNULL((SELECT 'TRUE' FROM TABLE2 WHERE TABLE2.ID = TABEL1.ID),'FALSE') AS columName,
etc
FROM TABLE1Stack Overflow用户
发布于 2011-10-18 17:48:09
SELECT Id, 'TRUE' AS NewFiled FROM TABEL1
INTERSECT
SELECT Id, 'TRUE' AS NewFiled FROM TABEL2
UNION
SELECT Id, 'FALSE' AS NewFiled FROM TABEL1
EXCEPT
SELECT Id, 'FALSE' AS NewFiled FROM TABEL2;Stack Overflow用户
发布于 2011-10-18 17:28:53
使用CASE语句，如下所示：
SELECT
T1.Id [Id]
,CASE WHEN T2.Id IS NOT NULL THEN 'TRUE' ELSE 'FALSE' END [Has Foreign Key in T2]
FROM
TABLE1 [T1]
LEFT OUTER JOIN
TABLE2 [T2]
ON
T2.Id = T1.Id页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/7805019
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