从合并后的“最大日期”获取值

Question

该查询有效，但是我想看看是否有更多的优化/更短的方法来获得相同的结果。 我想从3个表TABLE_01，TABLE_02，TABLE_03的联合中检索具有最大日期的所有数据。 无论哪个表具有最新的bill_date，我都希望检索该bill_date的行。 对于相同的PID和bill_date，它将总是返回多个行。

SELECT T1.PID, T1.BILL_DATE, T2.COL3, T2.COL4, T2.COL5
FROM
    (
     SELECT T.PID, MAX(T.BILL_DATE)
     FROM 
       ( 
         SELECT DISTINCT PID, BILL_DATE, COL3, COL4, COL5
         FROM TABLE_0501
         GROUP BY 1,2,3,4,5
         UNION ALL
         SELECT DISTINCT PID, BILL_DATE, COL3, COL4, COL5
         FROM TABLE_0502
         GROUP BY 1,2,3,4,5
         UNION ALL
         SELECT DISTINCT PID, BILL_DATE, COL3, COL4, COL5
         FROM TABLE_0503
         GROUP BY 1,2,3,4,5
        ) T
     GROUP BY 1  
    ) T1

INNER JOIN

    ( SELECT DISTINCT PID, BILL_DATE, COL3, COL4, COL5
      FROM TABLE_0501
      GROUP BY 1,2,3,4,5
      UNION ALL
      SELECT DISTINCT PID, BILL_DATE, COL3, COL4, COL5
      FROM TABLE_0501
      GROUP BY 1,2,3,4,5
      UNION ALL
      SELECT DISTINCT PID, BILL_DATE, COL3, COL4, COL5
      FROM TABLE_0501
      GROUP BY 1,2,3,4,5
    ) T2

ON T1.PID = T2.PID
AND T1.BILL_DATE = T2.BILL_DATE

Answer 1

是的，这里有一个QUALIFY子句很方便。

SELECT * FROM 
( 
    SELECT PID, BILL_DATE, COL3, COL4, COL5
    FROM TABLE_0501
    GROUP BY 1,2,3,4,5
    UNION ALL
    SELECT PID, BILL_DATE, COL3, COL4, COL5
    FROM TABLE_0502
    GROUP BY 1,2,3,4,5
    UNION ALL
    SELECT PID, BILL_DATE, COL3, COL4, COL5
    FROM TABLE_0503
    GROUP BY 1,2,3,4,5
) T
QUALIFY RANK() OVER (PARTITION BY PID ORDER BY BILL_DATE DESC) = 1;

在每组PID中，将从BILL_DATE到最低的行分配一个等级。 QUALIFY ... = 1将选择排名最高的BILL_DATE。