MySQL中的SUM函数使用教程

mysql/' target='_blank'>mysql的SUM函数是用来找出记录中各种的字段的总和。

要了解SUM函数考虑EMPLOYEE_TBL表具有以下记录：

MySQL> SELECT * FROM employee_tbl;+------+------+------------+--------------------+| id  | name | work_date | daily_typing_pages |+------+------+------------+--------------------+|  1 | John | 2007-01-24 |        250 ||  2 | Ram | 2007-05-27 |        220 ||  3 | Jack | 2007-05-06 |        170 ||  3 | Jack | 2007-04-06 |        100 ||  4 | Jill | 2007-04-06 |        220 ||  5 | Zara | 2007-06-06 |        300 ||  5 | Zara | 2007-02-06 |        350 |+------+------+------------+--------------------+7 rows in set (0.00 sec)

现在，假设根据上面的表想来计算所有的dialy_typing_pages的总数，那么可以通过使用下面的命令：

mysql> SELECT SUM(daily_typing_pages)  -> FROM employee_tbl;+-------------------------+| SUM(daily_typing_pages) |+-------------------------+|          1610 |+-------------------------+1 row in set (0.00 sec)

可以使用GROUP BY子句设置的各种记录的总和。下面的例子将总结所有相关的记录一个人，打印纸的每一个人总数。

mysql> SELECT name, SUM(daily_typing_pages)  -> FROM employee_tbl GROUP BY name;+------+-------------------------+| name | SUM(daily_typing_pages) |+------+-------------------------+| Jack |           270 || Jill |           220 || John |           250 || Ram |           220 || Zara |           650 |+------+-------------------------+5 rows in set (0.17 sec)