为什么此查询要求我在已有表格时声明表格？

Question

我的问题是，这个sproc中的最后一个查询是说我需要声明@N，但我已经有任何想法？

DECLARE @t TABLE 
    (Smpinstanceid UNIQUEIDENTIFIER) 

    INSERT INTO @t 

    (Smpinstanceid) 

    SELECT t.SmpInstanceid 
    FROM Tasks t 
    WHERE t.Completed IS NOT NULL and t.SmpInstanceID is not null 

DECLARE @N TABLE 
(SMPinstanceid UNIQUEIDENTIFIER,[Count] INT) 

INSERT INTO @N 
(SMPinstanceid,[COUNT]) 

    SELECT Smpinstanceid,COUNT (Smpinstanceid) AS [Count] 
         FROM @t 
         GROUP BY Smpinstanceid 




      UPDATE Tasks 
      SET StepNum = @n.Count 
      WHERE Tasks.SmpInstanceID = @n.smpinstanceid 
END 
GO 

Answer 1

没有参考在更新查询@n。您将需要使用子查询做你的更新，或以“从”条款（如果这是SQL Server）的

update tasks 
    SET StepNum = (select Count from @n 
        where Tasks.SmpInstanceID = @n.smpinstanceid) 

或

update tasks 
    set stepnum = n.count 
    from tasks 
    inner join @n as n 
     on (Tasks.SmpInstanceID = n.smpinstanceid) 

Answer 2

您需要将表放到WHERE子句中。

例如：

UPDATE T 
SET StepNum = n.[Count] 
FROM Tasks T 
INNER JOIN @n n ON n.SmpInstanceId = T.SmpInstanceId 

Answer 3

你@n声明，但它是一个表，并且不在Update子句中使用。您需要以某种方式将其添加到Update子句，或者您需要将其更改为不是表格。

UPDATE Tasks 
SET StepNum = @n.Count 
FROM Tasks 
JOIN @n on Tasks.SmpInstanceID = @n.smpinstanceid