MySQL SUM在同一个表上有多个GROUP BY

在MySQL的同一个表中,基于不同组的条件生成多个和结果的最佳方法是什么？

我相信我选择不好,但我无法找到更好的方法.

想象一下,我有一个订单表,我跟踪订单的客户,它的价值和订单的一些限定符(类型).我想对按订单类型组合分组的给定客户的总订单求和：

delimiter $$

CREATE TABLE `orders` (
  `idorder` int(11) NOT NULL,
  `value` double DEFAULT NULL,
  `idclient` int(11) DEFAULT NULL,
  `type1` int(11) DEFAULT NULL,
  `type2` int(11) DEFAULT NULL,
  `type3` bit(1) DEFAULT NULL,
  PRIMARY KEY (`idorder`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1$$

我的选择：

SELECT T0.idclient, T1.condition1, T2.condition2, T3.condition3 FROM
(SELECT 1 AS idclient) AS T0
LEFT JOIN
(SELECT idclient, SUM(value) condition1 FROM `test`.`orders` WHERE idclient = 1 AND type1 = 1 AND type2 = 1 AND type3 = 0) AS T1
ON T0.idclient = T1.idclient
LEFT JOIN
(SELECT idclient, SUM(value) condition2 FROM `test`.`orders` WHERE idclient = 1 AND type1 = 1 AND type2 = 1 AND type3 = 1) AS T2
ON T0.idclient = T2.idclient
LEFT JOIN
(SELECT idclient, SUM(value) condition3 FROM `test`.`orders` WHERE idclient = 1 AND type1 = 1 AND type2 = 0 AND type3 = 0) AS T3
ON T0.idclient = T3.idclient;

我错过了什么吗？

输出：

+----------+------------+------------+------------+
| idclient | condition1 | condition2 | condition3 |
+----------+------------+------------+------------+
|        1 |         10 |         20 |         30 |
+----------+------------+------------+------------+
1 row in set (0.00 sec)

数据：

INSERT INTO `orders` VALUES (1,5,1,1,1,'\0'),(2,5,1,1,1,'\0'),(3,20,1,1,1,''),(4,5,1,1,0,'\0'),(5,25,1,1,0,'\0');

解决方法:

我更像是一个SQL Server的人,但这是一个让你有动力的刺激.您可以使用CASE表达式来帮助某些订单类型的SUM()订单.

例如：

SELECT
    idclient AS [Client ID]
   ,COUNT(value) AS [Total Orders]
   ,SUM(value) AS [Total Order Value]
   ,SUM( CASE WHEN type1 = 'some type' THEN value ELSE 0 END) AS [Order Combo 1]
   ,SUM( CASE WHEN type1 = 'some type' AND type2 = 'another type' THEN value ELSE 0 END) [Order Combo 2]
   ,SUM( CASE WHEN type1 = 'some type' AND type2 = 'another type' AND type3 = 'another type' THEN value ELSE 0 END) [Order Combo 3]
FROM 'test'.'orders'
GROUP BY idclient

这将对[idclient]上的订单进行分组,并将SUM([value])分配给某些订单记录满足以下条件或您指定的组合的实例.

因此,如果客户有一个订单,其中[type1]是Apples而[type2]是Oranges,则可以在名为[Apple / Orange Orders]之类的新列下的SUM([value])为1.

结果还可以包括多个字段/列中相同记录的其他组合.如果这是一个问题,只需将CASE移动到GROUP BY,将每个组合分解为结果集中的单独记录.

希望这可以帮助！

标签：query-performance,mysql
来源： https://codeday.me/bug/20190806/1596945.html