How to use SQL GROUP BY?

GROUP BY keyword is used to group rows according to given columns.

Example: Get average grade of each class students belong to.

SELECT studentClass, AVG(grade) FROM studentGrades GROUP BY studentClass

How to use SQL HAVING?

HAVING keyword is used to filter rows returned by GROUP BY keyword. GROUP BY statement must be used in order to use HAVING to filter.

Example: Select class score averages greater than the 60.

SELECT studentClass, AVG(grade) FROM studentGrades GROUP BY studentClass HAVING AVG(grade) > 60