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要在MySQL中创建累积和列，您需要创建一个变量并将值设置为0。累积和会以当前值逐步递增下一个值。 首先，您需要在 SET 的帮助下创建一个变量。语法如下 - set @anyVariableName:= 0; 登录后复制 在 MySQL 中创建累积和列的语法如下 - select yourColumnName1,yourColumnName2,........N,(@anyVariableName := @anyVariableName + yourColumnName2) as anyVariableName
from yourTableName order by yourColumnName1; 登录后复制 为了理解上述概念，让我们创建一个表。以下是创建表的查询 - mysql> create table CumulativeSumDemo
−> (
−> BookId int,
−> BookPrice int
−> );
Query OK, 0 rows affected (0.67 sec) 登录后复制 借助select语句向表中插入一些记录。插入记录的查询如下 - mysql> insert into CumulativeSumDemo values(101,400);
Query OK, 1 row affected (0.15 sec)
mysql> insert into CumulativeSumDemo values(102,500);
Query OK, 1 row affected (0.16 sec)
mysql> insert into CumulativeSumDemo values(103,600);
Query OK, 1 row affected (0.16 sec)
mysql> insert into CumulativeSumDemo values(104,1000);
Query OK, 1 row affected (0.18 sec) 登录后复制 显示我借助插入命令插入的所有记录。查询如下 - mysql> select *from CumulativeSumDemo; 登录后复制 以下是输出 - +--------+-----------+
| BookId | BookPrice |
+--------+-----------+
| 101 | 400 |
| 102 | 500 |
| 103 | 600 |
| 104 | 1000 |
+--------+-----------+
4 rows in set (0.00 sec) 登录后复制 要添加累积和列，首先需要创建一个变量。查询如下 - mysql> set @CumulativeSum := 0;
Query OK, 0 rows affected (0.00 sec) 登录后复制 实现开头讨论的上述语法来添加累积和列。查询如下 - mysql> select BookId,BookPrice,(@CumulativeSum := @CumulativeSum + BookPrice) as CumSum
−> from CumulativeSumDemo order by BookId; 登录后复制 以下是输出。这里累积总和列也可见 - +--------+-----------+--------+
| BookId | BookPrice | CumSum |
+--------+-----------+--------+
| 101 | 400 | 400 |
| 102 | 500 | 900 |
| 103 | 600 | 1500 |
| 104 | 1000 | 2500 |
+--------+-----------+--------+
4 rows in set (0.00 sec) 登录后复制 |
