⟩ What Are Group Functions in Query Statements in MS SQL Server?
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.
* SUM(exp) - Returns the sum value of the expression evaluated on each row of the group.
* COUNTDISTINCT(exp) - Returns the number of distinct values of the expression evaluated on each row of the group.
