What are the benefits of using the MySQL SUM() function with the GROUP BY clause?

When we use the MySQL SUM() function with the GROUP BY clause, the SUM() function calculates the sum of each group specified in the GROUP BY clause . The benefit of using SUM() with GROUP BY clause is that we can easily find the total for a specific group. To understand the above concept, consider an "employee_tbl" table which 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)

The following query will aggregate all the records related to a person and you will get the total number of pages entered by each person.

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)

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