使用WITH语句时无法定义SQL变量

Question

这个sql是有效的:

 WITH A AS
 (SELECT TOP 1000 * 
  FROM dbo.SomeTable)

 SELECT * FROM A

虽然这个给出错误(关键字'DECLARE'附近的语法不正确):

WITH A AS
(SELECT TOP 1000 * 
 FROM dbo.SomeTable)

 DECLARE @dt DATETIME 

 SET @dt = GETDATE()
 SELECT * FROM A

 PRINT DATEDIFF(SS,GETDATE(),@dt)

为什么？

Answer 1

做就是了

DECLARE @dt DATETIME;

SET @dt = GETDATE();

WITH A
     AS (SELECT TOP 1000 *
         FROM   dbo.SomeTable)
SELECT *
FROM   A;

PRINT DATEDIFF(SS, GETDATE(), @dt);

CTE定义后唯一有效的东西是使用它的单个语句