爲什麼此查詢要求我在已有表格時聲明表格？

Question

我的問題是，這個sproc中的最後一個查詢是說我需要聲明@N，但我已經有任何想法？

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

沒有參考在更新查詢@n。您將需要使用子查詢做你的更新，或以「從」條款（如果這是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

您需要將表放到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聲明，但它是一個表，並且不在Update子句中使用。您需要以某種方式將其添加到Update子句，或者您需要將其更改爲不是表格。

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