Question

请考虑此查询：

SELECT tesd.State_Code,
   tesd.City_Code,
   tesd.Row_ID,
   tesd.Qsno,
   tesd.Total_Period,
   tesd.Current_Period,
   tesd.Week,
   tesd.Block_No,
   tesd.Family_ID,
   tesd.Line_ID,
   tesd.Page_ID
   INTO #tmp
FROM   Specification_Master tesm
   INNER JOIN Specification_Details tesd
        ON  tesd.Master_Id = tesm.Id
WHERE  tesm.[Year] = 2000
   AND tesm.[Month] = 10
   AND tesd.City_Code IN ('001')

我从2个表中查询了一些数据并将它们插入到#tmp中。然后我想从其他2个表中选择数据并检查其中一个表的值是否为#tmp tbale：

SELECT *
FROM   tbl_Details D
   INNER JOIN tbl_Master tem
        ON  D.ID_Master = tem.Id
WHERE  D.Period <= 5
 AND EXISTS (
           SELECT Row_ID
           FROM   #tmp tm
           WHERE  tm.Current_Period > 1
                  AND tm.State_Code = tem.State_Code
                  AND tm.City_Code = tem.City_Code
                  AND tm.Qsno = tem.Qsno
       )
   AND D.[Status] > 2

当我运行此查询时，我只有一行，但当我将EXISTS更改为NOT EXISTS时，我获得了更多行。我单独运行此查询：

SELECT Row_ID
           FROM   #tmp tm,tbl_Master tem 
           WHERE  tm.Current_Period > 1
                  AND tm.Ostan_Code = tem.State_Code
                  AND tm.City_Code = tem.City_Code
                  AND tm.Porseshname_ID = tem.Qsno

并返回30行。为什么Exists有这样的行为？

Answer 1

Exists根据子查询的结果返回一个布尔值。重要的不是返回1行或30行。您要检索的行数基于select *语句，而不是Exists子句。

where子句中存在返回错误结果

1 个答案: