**A**ggregate functions are the function that is used to compute against a “returned column of numeric data” from your select statement. Aggregate functions basically summarize the results of a particular column of selected data. In aggregate function the values of multiple rows are grouped together as input on certain criteria to form a single value of more significant meaning or measurement such as a set, a bag or a list. All aggregate functions will ignore NULL values.

**Most commonly used SQL aggregate functions are **

**MIN** : Returns the smallest value in a given column.

**MAX** : Returns the largest value in a given column.

**SUM** : Returns the sum of the numeric values in a given column.

**AVG** : Returns the average value of a given column.

**COUNT** : Returns the total number of values in a given column.

**COUNT(*)** : Returns the number of rows in a table.

**GROUPING** : Is a column or an expression that contains a column in a GROUP BY clause.

**STDEV** : Returns the statistical standard deviation of all values in the specified expression.

**STDEVP** : Returns the statistical standard deviation for the population for all values in the specified expression.

**VAR** : Returns the statistical variance of all values in the specified expression, may be followed by the OVER clause.

**VARP** : Returns the statistical variance for the population for all values in the specified expression.