sql – 将IF EXISTS与CTE一起使用

我想检查CTE表是否有记录或null.但我总是收到错误信息’关键字’IF’附近的SQL语法错误,如下面的SQL.现在ADMISSION_OUTSIDE TABLE中没有匹配的记录. SQl的结果应该打印’NOT OK’.谢谢,

WITH ADMISSION_OUTSIDE AS 
(   .....
.....
)

IF EXISTS (SELECT * FROM ADMISSION_OUTSIDE)
PRINT 'OK'
ELSE PRINT 'NOT OK'

解决方法

A CTE must be followed by a single SELECT,INSERT,UPDATE,or DELETE
statement that references some or all the CTE columns

它可以像这样重写

WITH ADMISSION_OUTSIDE AS 
(   .....
.....
)
SELECT 'OK' WHERE EXISTS (SELECT * FROM ADMISSION_OUTSIDE)
UNION ALL
SELECT 'NOT OK' WHERE NOT EXISTS (SELECT * FROM ADMISSION_OUTSIDE)

这是一个演示

;WITH CTE AS
(
SELECT 1 as a WHERE 1=0
)
SELECT 'OK' WHERE EXISTS (SELECT * FROM CTE)
UNION ALL
SELECT 'NOT OK' WHERE NOT EXISTS (SELECT * FROM CTE)

结果：不行

;WITH CTE AS
(
SELECT 1 as a WHERE 1=1
)
SELECT 'OK' WHERE EXISTS (SELECT * FROM CTE)
UNION ALL
SELECT 'NOT OK' WHERE NOT EXISTS (SELECT * FROM CTE)

结果：好的

（编辑：源码网）

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