collect data from multiple records and group the result by one or more column. It is generally used in a SELECT statement.
mysql> select category, count(*) from myposts group by category;
+------------------------------+----------+
| category | count(*) |
+------------------------------+----------+
| | 332 |
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+------------------------------+----------+
38 rows in set (0.00 sec)You can also use some aggregate functions like COUNT, SUM, MIN, MAX, AVG, etc. on the grouped column.
aggregate_function: It specifies a function such as SUM, COUNT, MIN, MAX, or AVG etc. tables: It specifies the tables, from where you want to retrieve the records. There must be at least one table listed in the FROM clause.
WHERE conditions: It is optional. It specifies the conditions that must be fulfilled for the records to be selected.
SELECT emp_name, SUM(working_hours) AS "Total working hours"
FROM employees
GROUP BY emp_name; 