SQL Aggregate Functions

David Haertzen David Haertzen, Tutorial Author
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SQL > SQL Advanced > SQL Aggregate Functions

What are SQL Aggregate Functions?

The SQL Aggregate Functions are functions that provide mathematical operations. If you need to add, count or perform basic statistics, these functions will be of great help.  

The functions include:

  • count() - counts a number of rows
  • sum() - compute sum
  • avg() - compute average
  • min() - compute minimum
  • max() - compute maximum

Why Use SQL Aggregate Functions?

The SQL Aggregate Functions are useful when mathematical operations must be performed on all or a grouping of values.

How To Use SQL Aggregate Functions

SQL Aggregate Functions are used as follows. If a grouping of values is needed also include the GROUP BY clause.

Use a column name or expression as the parameter to the Aggregate Function. The parameter, '*', represents all rows.

SQL Aggregate Functions Syntax

SELECT <column_name1>, <column_name2> <aggregate_function(s)>
FROM <table_name>
GROUP BY <column_name1>, <column_name2>

SQL Aggregate Functions Example

The following example Aggregate Functions are applied to the employee_count of the branch table. The region_nbr is the level of grouping.

Here are the contents of the table:

108New York10010
404San Diego4006
415San Jose4003

This SQL Statement with aggregate functions is executed:

SELECT region_nbr, count(branch_nbr), sum(employee_count), min(employee_count),
max(employee_count), avg(employee_count)
FROM dbo.branch
GROUP BY region_nbr
ORDER BY region_nbr

Here is the result.

sum (employee_count)min

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