Question

我有一张这样的表：

orderno       insurance
ABC123        3.00
ABC123        3.00
ABC123        3.00
DEF456        2.00
DEF456        2.00

我想得到每个独特订单的平均保险价值总和。

e.g。 (3.00+3.00+3.00)/3 + (2.00+2.00)/2

= 5

如何使用MySQL查询实现此目的？

Answer 1

试试这个：

SELECT SUM(avgIns) AS oAverage
FROM
    (SELECT OrderNo, AVG(Insurance) AS avgIns
    FROM yourTableName
    GROUP BY OrderNo) iTable

<强>更新

如果您想限制小数位，请使用 FORMAT（value，decimalPlaces）

SELECT FORMAT(SUM(avgIns),2) AS oAverage         -- Returns two decimal places
FROM
    (SELECT OrderNo, AVG(Insurance) AS avgIns
    FROM yourTableName
    GROUP BY OrderNo) iTable

Answer 2

select sum(value) from (
    select sum(insurance) / count(insurance) as value
    from yourTableName
    group by insurance
) temp;

在mysql中运行示例：

mysql> create table testTable (id int primary key auto_increment, orderno varchar(12), insurance decimal(6, 2));
Query OK, 0 rows affected (0.27 sec)


mysql> insert into testTable (orderno, insurance) values ('ABC123', 3), ('ABC123', 3), ('ABC123', 3), ('DEF456', 2), ('DEF456', 2);
Query OK, 5 rows affected (0.00 sec) Records: 5  Duplicates: 0  Warnings: 0


mysql> select * from testTable;
+----+---------+-----------+
| id | orderno | insurance |
+----+---------+-----------+
|  1 | ABC123  |      3.00 |
|  2 | ABC123  |      3.00 |
|  3 | ABC123  |      3.00 |
|  4 | DEF456  |      2.00 |
|  5 | DEF456  |      2.00 |
+----+---------+-----------+
5 rows in set (0.00 sec)


mysql> select sum(value) from (     
select sum(insurance) / count(insurance) as value
from testTable
group by insurance ) temp;
+------------+
| sum(value) |
+------------+
|   5.000000 |
+------------+
1 row in set (0.02 sec)

mysql使用计算列值选择查询

2 个答案: