sql-aggregates

Question 1

What are some examples of aggregate functions?

Answer 1

Max() : Computes the maximum of the non-null input values.
Avg(): Computes the average (arithmetic mean) of all the non-null input values.
Count(*): Computes the number of input rows.
Count(“any”): Computes the number of input rows in which the input value is not null.

Question 2

What is the purpose of a group by clause?

Answer 2

To divide rows returned from the select statement into groups.