MySQL中的SUM函数使用教程

时间:2022-09-11 14:27:43

MySQLSUM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:

?
1
2
3
4
5
6
7
8
9
10
11
12
13
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:

?
1
2
3
4
5
6
7
8
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。

?
1
2
3
4
5
6
7
8
9
10
11
12
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)