Tutorial _ MySQL

This article mainly introduces the use of the SUM function in MySQL, which is the basic knowledge in MySQL beginners, you can refer to MySQL's SUM function to find the SUM of various fields in the record.

To understand the SUM function, consider that the EMPLOYEE_TBL table has the following records:

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)

Now, if you want to calculate the total number of all dialy_typing_pages based on the preceding table, you can use the following command:

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

You can use the group by clause to set the total number of records. The following example summarizes the total number of people who record a person and print paper.

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)