使用子查询比较两个表？

Question

我可以使用以下查询比较两个表的缺失数据

 SELECT S.DEVID,S.INPUTID,S.PRI,S.CCID FROM [DEVICE-SECURITY].DBO.DEVICE_LINK S
  WHERE HID = 4 
  EXCEPT 
  SELECT  T.DEVID,T.INPUTID,T.PRI,T.CCID  FROM  DEVICE-CONFIG.DBO.DEVICE_LINK T
  WHERE HID = 1

The above query returns four rows which are not present in my source table

现在我正在尝试使用子查询来获得相同的结果

 SELECT  S.DEVID,S.INPUTID,S.PRI,S.CCID , 
 CASE WHEN S.HID = '4' THEN '1'  END AS HID 
 FROM  [DEVICE-SECURITY].DBO.DEVICE_LINK S
  WHERE S.HID= 4 AND  NOT EXISTS    (
 SELECT T.DEVID,T.INPUTID,T.PRI,T.CCID FROM DEVICE-CONFIG.DBO.DEVICE_LINK  T
   WHERE T.HID = 1 )

It returns no rows .

如何使用子查询获得同样的结果

Answer 1

等效的不存在查询是

SELECT S.DEVID,S.INPUTID,S.PRI,S.CCID FROM [DEVICE-SECURITY].DBO.DEVICE_LINK S
  WHERE HID = 4 
  AND NOT EXISTS (
    SELECT 1 FROM  DEVICE-CONFIG.DBO.DEVICE_LINK T
    WHERE HID = 1 
    AND T.DEVID = S.DEVID AND T.INPUTID = S.INPUTID
    AND T.PRI = S.PRI AND T.CCID = S.CCID
)

Answer 2

你有两个选择

你可以做一个 not in 过滤器，这样子查询就不必连接到外部

SELECT S.DEVID,S.INPUTID,S.PRI,S.CCID , CASE WHEN S.HID = '4' THEN '1' END AS HID FROM [DEVICE-SECURITY].DBO.DEVICE_LINK S WHERE S.HID= 4 AND  S.DEVID+S.INPUTID+S.PRI+S.CCID NOT in ( SELECT T.DEVID+T.INPUTID+T.PRI+T.CCID FROM DEVICE-CONFIG.DBO.DEVICE_LINK T WHERE T.HID = 1 )

或者您可以保持不存在，并通过您要比较的所有字段将子查询连接到主查询

SELECT S.DEVID,S.INPUTID,S.PRI,S.CCID , CASE WHEN S.HID = '4' THEN '1' END AS HID FROM [DEVICE-SECURITY].DBO.DEVICE_LINK S WHERE S.HID= 4 AND  NOT exists ( SELECT 1 FROM DEVICE-CONFIG.DBO.DEVICE_LINK T WHERE T.HID = 1  and T.DEVID+T.INPUTID+T.PRI+T.CCID=S.DEVID+S.INPUTID+S.PRI+S.CCID)

使用子查询比较两个表？

Comparing two tables using sub query ?

sql

sql-server

case

subquery

where-clause