单排变量

Question

我被困在这个地方。我试图获得一个单一的行集值在一个变量。

DECLARE @last_timestamp as varchar; 
SET @last_timestamp = SELECT MAX(modify_timestamp) FROM dbo.table1 
PRINT @last_timestamp 

它返回下面的错误

Msg 156, Level 15, State 1, Line 2 
Incorrect syntax near the keyword 'SELECT'. 

是光标对这个问题的唯一解决方案。任何帮助将有所帮助？

Answer 1

尝试：

DECLARE @last_timestamp as varchar; 
SELECT @last_timestamp = MAX(modify_timestamp) FROM dbo.table1 
PRINT @last_timestamp 

或

DECLARE @last_timestamp as varchar; 
SET @last_timestamp = (SELECT MAX(modify_timestamp) FROM dbo.table1) 
PRINT @last_timestamp 

Answer 2

SELECT @last_timestamp := MAX(modify_timestamp) FROM dbo.table1 

或

SELECT MAX(modify_timestamp) INTO @last_timestamp FROM dbo.table1 

或

SET @last_timestamp = (SELECT MAX(modify_timestamp) FROM dbo.table1) 

Answer 3

您可以将parenthese围绕SELECT声明

DECLARE @last_timestamp as varchar; 
SET @last_timestamp = (SELECT MAX(modify_timestamp) FROM dbo.table1) 
PRINT @last_timestamp