我们如何使用MySQL SUM()函数?
MySQL SUM函数用于找出各种记录中一个字段的总和。为了理解SUM()
方法,请考虑一个“ employee_tbl”表,该表具有以下记录-
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,假设基于上表您要计算所有dialy_typing_pages的总数,那么您可以使用以下命令进行计算-
mysql> SELECT SUM(daily_typing_pages)-> FROM employee_tbl;
+-------------------------+
| SUM(daily_typing_pages) |
+-------------------------+
| 1610 |
+-------------------------+
1 row in set (0.00 sec)
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