jcadima
6/2/2015 - 3:50 AM

MySQL GROUP BY

MySQL GROUP BY

reference:
http://www.tutorialspoint.com/mysql/mysql-group-by-clause.htm

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 |
+------+------+------------+--------------------+


we want to display total number of pages typed by each person separately. 
This is done by using aggregate functions in conjunction with a GROUP BY clause as follows:

mysql> SELECT name, COUNT(*)
    -> FROM   employee_tbl 
    -> GROUP BY name;
+------+----------+
| name | COUNT(*) |
+------+----------+
| Jack |        2 |
| Jill |        1 |
| John |        1 |
| Ram  |        1 |
| Zara |        2 |
+------+----------+