根据当前行的日期从另一个表中获取最大日期答案

【问题标题】：Get max date from another table based on date of current row根据当前行的日期从另一个表中获取最大日期
【发布时间】：2018-11-30 10:40:42
【问题描述】：

我有两张桌子，CALL_DATA 和 MASTER_DATA。

主数据有一个客户的日常数据，CALL_DATA 有一些客户的电话以及其他一些数据。我想为每个客户和他在MASTER_DATA 中的每一行获取最近日期（到现在为止的最大日期）从CALL_DATA 开始的行。

我想出了这个：

SELECT MAX(CALL_DATA.CALL_DATE) OVER (PARTITION BY MASTER_DATA.CUSTOMER_ID 
                                          ORDER BY MASTER_DATA.DAILY_START_DATE)
        AS max_date_agg
     , MASTER_DATA.*
     , CALL_DATA.*
  FROM MASTER_DATA, CALL_DATA
 WHERE CALL_DATA.CALL_DAT <= MASTER_DATA.DAILY_START_DATE 
   AND CALL_DATA.CUSTOMER_ID = MASTER_DATA.CUSTOMER_ID;

但这让我在每天的开始日期都有不止一个现场直播。事实上，它返回的行数与CALL_DATA 表中的行数一样多，直到MASTER_DATA 中的DAILY_START_DATE。

例子：

   MAX_DATE_AGG             CUSTOMER_ID  DAILY_START_DATE
24/10/17 00:00:00,000000000 100664970   24/10/17 00:00:00
24/10/17 00:00:00,000000000 100664970   25/10/17 00:00:00
24/10/17 00:00:00,000000000 100664970   26/10/17 00:00:00
24/10/17 00:00:00,000000000 100664970   27/10/17 00:00:00
24/10/17 00:00:00,000000000 100664970   28/10/17 00:00:00
24/10/17 00:00:00,000000000 100664970   29/10/17 00:00:00
24/10/17 00:00:00,000000000 100664970   30/10/17 00:00:00
24/10/17 00:00:00,000000000 100664970   31/10/17 00:00:00
24/10/17 00:00:00,000000000 100664970   01/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   02/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   03/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   04/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   05/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   06/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   07/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   08/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   09/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   10/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   11/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   12/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   13/11/17 00:00:00
24/10/17 00:00:00,000000000 100664970   14/11/17 00:00:00
15/11/17 00:00:00,000000000 100664970   15/11/17 00:00:00
15/11/17 00:00:00,000000000 100664970   15/11/17 00:00:00
15/11/17 00:00:00,000000000 100664970   16/11/17 00:00:00
15/11/17 00:00:00,000000000 100664970   16/11/17 00:00:00
15/11/17 00:00:00,000000000 100664970   17/11/17 00:00:00
15/11/17 00:00:00,000000000 100664970   17/11/17 00:00:00
15/11/17 00:00:00,000000000 100664970   18/11/17 00:00:00
15/11/17 00:00:00,000000000 100664970   18/11/17 00:00:00

【问题讨论】：

标签： sql oracle datetime

【解决方案1】：

您可以将您的查询转换为相关子查询：

SELECT MASTER_DATA.*, (
    SELECT MAX(CALL_DATE)
    FROM CALL_DATA
    WHERE CALL_DATA.CUSTOMER_ID = MASTER_DATA.CUSTOMER_ID
    AND CALL_DATA.CALL_DAT <= MASTER_DATA.DAILY_START_DATE
) AS MOST_RECENT_CALL_TILL_NOW
FROM MASTER_DATA

【讨论】：

【解决方案2】：

这个查询应该返回你想要的

SELECT T.*
  FROM (
          SELECT RANK() OVER (PARTITION BY MASTER_DATA.CUSTOMER_ID, MASTER_DATA.DAILY_START_DATE ORDER BY CALL_DATA.CALL_DATE DESC) AS myrank,
                MASTER_DATA.CUSTOMER_ID,
                MASTER_DATA.DAILY_START_DATE,
                CALL_DATA.CALL_DATE
           FROM MASTER_DATA,
                CALL_DATA
          WHERE CALL_DATA.CALL_DATE   <= MASTER_DATA.DAILY_START_DATE 
            AND CALL_DATA.CUSTOMER_ID = MASTER_DATA.CUSTOMER_ID
       ) T
 WHERE myrank = 1  
  ;

【讨论】：