Group functions are functions applied to a group of rows. Examples of group functions are:

* COUNT(*) - Returns the number of rows in the group.

* MIN(exp) - Returns the minimum value of the expression evaluated on each row of the group.

* MAX(exp) - Returns the maximum value of the expression evaluated on each row of the group.

* AVG(exp) - Returns the average value of the expression evaluated on each row of the group.