aggregate-functions-transact-sql.md

title	Aggregate Functions (Transact-SQL)
description	Aggregate Functions (Transact-SQL)
author	markingmyname
ms.author	maghan
ms.date	08/15/2018
ms.service	sql
ms.subservice	t-sql
ms.topic	reference
ms.custom	ignite-2025
helpviewer_keywords	functions [SQL Server], aggregate aggregate functions [SQL Server], about aggregate functions summarizing functions aggregate functions [SQL Server]
dev_langs	TSQL
monikerRange	>=aps-pdw-2016 || =azuresqldb-current || =azure-sqldw-latest || >=sql-server-2016 || >=sql-server-linux-2017 || =azuresqldb-mi-current || =fabric || =fabric-sqldb

Aggregate Functions (Transact-SQL)

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An aggregate function performs a calculation on a set of values, and returns a single value. Except for COUNT(*), aggregate functions ignore null values. Aggregate functions are often used with the GROUP BY clause of the SELECT statement.

All aggregate functions are deterministic. In other words, aggregate functions return the same value each time that they are called, when called with a specific set of input values. See Deterministic and Nondeterministic Functions for more information about function determinism. The OVER clause may follow all aggregate functions, except the STRING_AGG, GROUPING or GROUPING_ID functions.

Use aggregate functions as expressions only in the following situations:

• The select list of a SELECT statement (either a subquery or an outer query).
• A HAVING clause.

[!INCLUDEtsql] provides the following aggregate functions:

• APPROX_COUNT_DISTINCT
• AVG
• CHECKSUM_AGG
• COUNT
• COUNT_BIG
• GROUPING
• GROUPING_ID
• MAX
• MIN
• STDEV
• STDEVP
• STRING_AGG
• SUM
• VAR
• VARP

See also

Built-in Functions (Transact-SQL)
OVER Clause (Transact-SQL)