Question

不确定这是否是最好的方法，但我会尝试举例解释我想要完成的事情。我有大约4或5个不同的表，每个表包含一个TOTAL字段。一个表包含CUSTOMER_ID（其中4个或5个表中的每个表都包含一个将其记录链接到父CUSTOMER表的外键）。

我希望在查询的一列中按CUSTOMER_ID进行分组，而其他每列都包含相应表格的总计。

这有意义吗？我正在寻找最有效和设计合理的查询。听起来我需要子查询而不是一堆左外连接？

Answer 1

SELECT  C.CUSTOMER_ID,
        T1.TOTAL TOTAL_T1,
        T2.TOTAL TOTAL_T2,
        T3.TOTAL TOTAL_T3,
        T4.TOTAL TOTAL_T4,
        T5.TOTAL TOTAL_T5
FROM CUSTOMER C
LEFT JOIN ( SELECT CUSTOMER_ID, SUM(TOTAL) TOTAL)
            FROM TABLE1
            GROUP BY CUSTOMER_ID) T1
    ON C.CUSTOMER_ID = T1.CUSTOMER_ID
LEFT JOIN ( SELECT CUSTOMER_ID, SUM(TOTAL) TOTAL)
            FROM TABLE2
            GROUP BY CUSTOMER_ID) T2
    ON C.CUSTOMER_ID = T2.CUSTOMER_ID
LEFT JOIN ( SELECT CUSTOMER_ID, SUM(TOTAL) TOTAL)
            FROM TABLE3
            GROUP BY CUSTOMER_ID) T3
    ON C.CUSTOMER_ID = T3.CUSTOMER_ID
LEFT JOIN ( SELECT CUSTOMER_ID, SUM(TOTAL) TOTAL)
            FROM TABLE4
            GROUP BY CUSTOMER_ID) T4
    ON C.CUSTOMER_ID = T4.CUSTOMER_ID
LEFT JOIN ( SELECT CUSTOMER_ID, SUM(TOTAL) TOTAL)
            FROM TABLE5
            GROUP BY CUSTOMER_ID) T5
    ON C.CUSTOMER_ID = T5.CUSTOMER_ID

Answer 2

不确定我是否正确地得到了你想要的东西，但我认为你可以用简单的连接来完成这个，对于两个表

select table1.customerId, sum(table1.total) as total1, sum(table2.total) as total2
FROM table1, table2
where table1.customerId=table2.customerId
group by table1.customerId;

您可以根据需要使用任意数量的表格

Answer 3

这是另一种可能性。它不需要派生任何表格然后加入它们。这应该也足够有效，假设table1-table5上的FK是CUSTOMER_ID ......虽然不是100％肯定。另外根据我离开加入时的经验，使用ISNULL通常是一个好主意，所以你总是得到一些数值（尽管在这种情况下，这是我的另一个假设）。希望这有帮助！

SELECT  
C.CUSTOMER_ID,
    ISNULL(SUM(T1.TOTAL), 0) AS TOTAL_T1,
    ISNULL(SUM(T2.TOTAL), 0) AS TOTAL_T2,
    ISNULL(SUM(T3.TOTAL), 0) AS TOTAL_T3,
    ISNULL(SUM(T4.TOTAL), 0) AS TOTAL_T4,
    ISNULL(SUM(T5.TOTAL), 0) AS TOTAL_T5
FROM CUSTOMER C
    LEFT JOIN TABLE1 T1 ON C.CUSTOMER_ID = T1.CUSTOMER_ID
    LEFT JOIN TABLE2 T2 ON C.CUSTOMER_ID = T2.CUSTOMER_ID
    LEFT JOIN TABLE3 T3 ON C.CUSTOMER_ID = T3.CUSTOMER_ID
    LEFT JOIN TABLE4 T4 ON C.CUSTOMER_ID = T4.CUSTOMER_ID
    LEFT JOIN TABLE5 T5 ON C.CUSTOMER_ID = T5.CUSTOMER_ID
GROUP BY C.CUSTOMER_ID

单个查询中来自不同表的总计的SQL SUM

3 个答案: