Question

我想在Java代码中使用此查询：

DECLARE @BRPS BIGINT
SELECT @BRPS=cntr_value 
FROM sys.dm_os_performance_counters
WHERE counter_name LIKE 'Batch Requests/sec%'
WAITFOR DELAY '000:00:10'
SELECT (cntr_value-@BRPS)/10.0 AS "Batch Requests/sec"
FROM sys.dm_os_performance_counters
WHERE counter_name LIKE 'Batch Requests/sec%'

当我删除DECLARE @BRPS BIGINT时，我收到错误消息。你能帮我把这段代码重写成简单的SQL查询吗？同样的结果呢？

Answer 1

那里有很多瑕疵......

首先：不，如果您想将值存储到稍后要使用的变量中，则无法删除DECLARE。

第二：如果将值写入变量，则结果必须是标量。这意味着：一行中的一列。使用LIKE 'Batch Requests/sec%'看起来你期望得到几个可能的结果......试试吧

DECLARE @BRPS BIGINT=(SELECT cntr_value 
                      FROM sys.dm_os_performance_counters
                      WHERE counter_name = 'Batch Requests/sec');

SELECT @BRPS;

第三：你期待什么？尝试：

SELECT cntr_value FROM sys.dm_os_performance_counters WHERE counter_name = 'Batch Requests/sec';
WAITFOR DELAY '000:00:10';
SELECT cntr_value FROM sys.dm_os_performance_counters WHERE counter_name = 'Batch Requests/sec';
GO
SELECT cntr_value FROM sys.dm_os_performance_counters WHERE counter_name = 'Batch Requests/sec';
GO
SELECT cntr_value FROM sys.dm_os_performance_counters WHERE counter_name = 'Batch Requests/sec';

第四：你想要达到什么目标？

Answer 2

DECLARE @ctn VARBINARY(128)
SELECT @ctn = CAST(cntr_value AS BINARY(8)) 
FROM sys.dm_os_performance_counters
WHERE counter_name LIKE 'Batch Requests/sec%'
SET CONTEXT_INFO @ctn

GO ----

SELECT [Batch Requests/sec] = (cntr_value - CAST(SUBSTRING(CONTEXT_INFO(), 1, 8) AS BIGINT)) / 10.
FROM sys.dm_os_performance_counters
WHERE counter_name LIKE 'Batch Requests/sec%'

我可以删除DECLARE @BRPS BIGINT

2 个答案: