SQL 查询以查找从中选择记录的同一个表

Question

样本记录：

Custid pref_location
C1     PUNE
C1     MUMBAI
c1     DELHI    
C2     PUNE
C2     MUMBAI
C3     MUMBAI  
c4     PUNE
C5     DELHI

我想获取首选项位置仅为 PUNE 或 MUMBAI 的记录。我在以下查询的帮助下进行：

SELECT *
FROM EMP_PRE_LOCATION E1
WHERE EXISTS (SELECT 1 
        FROM EMP_PRE_LOCATION E2 
        WHERE E2.EID=E1.EID AND E2.PRE_LOCATION in ('PUNE','MUMBAI'))
AND NOT  EXISTS (SELECT 1 
        FROM EMP_PRE_LOCATION E3 
        WHERE E3.EID=E1.EID AND E3.PRE_LOCATION NOT in('PUNE','MUMBAI'));

他们有更好的方法来达到同样的效果吗？

Answer 1

我想你只是想要：

SELECT E1.*
FROM EMP_PRE_LOCATION E1
WHERE NOT EXISTS (SELECT 1 
                  FROM EMP_PRE_LOCATION E2 
                  WHERE E2.EID = E1.EID AND
                        E2.PRE_LOCATION NOT IN ('PUNE', 'MUMBAI')
                 );

如果您只希望员工在这两个位置，那么您可以使用GROUP BY 和HAVING：

SELECT E1.EID
FROM EMP_PRE_LOCATION E1
GROUP BY E1.EID
HAVING SUM(CASE WHEN E1.PRE_LOCATION NOT IN ('PUNE', 'MUMBAI') THEN 1 ELSE 0 END) = 0;

如果您想要位置列表，可以添加LISTAGG(E1.PRE_LOCATION, ',')。

Answer 2

请试试这个。

SELECT *
FROM EMP_PRE_LOCATION
WHERE pref_location ='PUNE' OR pref_location ='MUMBAI'

Answer 3

第二个WHERE 子句可以满足你的要求：

SELECT E1.*
FROM EMP_PRE_LOCATION E1
WHERE E1.PRE_LOCATION IN ('PUNE','MUMBAI') AND 
      NOT EXISTS (SELECT 1 
                  FROM EMP_PRE_LOCATION E3 
                  WHERE E3.EID = E1.EID AND E3.PRE_LOCATION NOT IN ('PUNE','MUMBAI')
                 );

这将只返回EIDs，其中只有LOCATION IN ('PUNE','MUMBAI')。