AVG (Transact-SQL)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Azure Synapse Analytics
Analytics Platform System (PDW)
SQL analytics endpoint in Microsoft Fabric
Warehouse in Microsoft Fabric
This function returns the average of the values in a group. It ignores null values.
Transact-SQL syntax conventions
Syntax
AVG ( [ ALL | DISTINCT ] expression )
[ OVER ( [ partition_by_clause ] order_by_clause ) ]
Arguments
ALL
Applies the aggregate function to all values. ALL is the default.
DISTINCT
Specifies that AVG operates only on one unique instance of each value, regardless of how many times that value occurs.
expression
An expression of the exact numeric or approximate numeric data type category, except for the bit data type. Aggregate functions and subqueries aren't permitted.
OVER ( [ partition_by_clause ] order_by_clause)
partition_by_clause divides the result set produced by the FROM clause into partitions to which the function is applied. If not specified, the function treats all rows of the query result set as a single group. The order_by_clause determines the logical order in which the operation is performed. The order_by_clause is required. For more information, see OVER Clause (Transact-SQL).
Return types
The evaluated result of expression determines the return type.
| Expression result | Return type |
|---|---|
| tinyint | int |
| smallint | int |
| int | int |
| bigint | bigint |
| decimal category (p, s) | decimal(38, max(s,6)) |
| money and smallmoney category | money |
| float and real category | float |
Remarks
If the data type of expression is an alias data type, the return type is also of the alias data type. However, if the base data type of the alias data type is promoted, for example from tinyint to int, the return value takes the promoted data type, and not the alias data type.
AVG () computes the average of a set of values by dividing the sum of those values by the count of non-null values. If the sum exceeds the maximum value for the data type of the return value, AVG() returns an error.
AVG is a deterministic function when used without the OVER and ORDER BY clauses. It's nondeterministic when specified with the OVER and ORDER BY clauses. For more information, see Deterministic and Nondeterministic Functions. Also, AVG may appear to behave as a nondeterministic function when you use it with float and real data types. But the underlying reason is the approximate nature of these data types.
Examples
A. Using the SUM and AVG functions for calculations
This example calculates the average vacation hours, and the sum of sick leave hours, that the vice presidents of Adventure Works Cycles have used. Each of these aggregate functions produces a single summary value for all the retrieved rows. The example uses the AdventureWorks2022 database.
SELECT AVG(VacationHours)AS 'Average vacation hours',
SUM(SickLeaveHours) AS 'Total sick leave hours'
FROM HumanResources.Employee
WHERE JobTitle LIKE 'Vice President%';
Here's the result set.
Average vacation hours Total sick leave hours
---------------------- ----------------------
25 97
(1 row(s) affected)
B. Using the SUM and AVG functions with a GROUP BY clause
When used with a GROUP BY clause, each aggregate function produces a single value covering each group, instead of a single value covering the whole table. The following example produces summary values for each sales territory in the AdventureWorks2022 database. The summary lists the average bonus received by the sales people in each territory, and the sum of year-to-date sales for each territory.
SELECT TerritoryID, AVG(Bonus)as 'Average bonus', SUM(SalesYTD) as 'YTD sales'
FROM Sales.SalesPerson
GROUP BY TerritoryID;
GO
Here's the result set.
TerritoryID Average Bonus YTD Sales
----------- --------------------- ---------------------
NULL 0.00 1252127.9471
1 4133.3333 4502152.2674
2 4100.00 3763178.1787
3 2500.00 3189418.3662
4 2775.00 6709904.1666
5 6700.00 2315185.611
6 2750.00 4058260.1825
7 985.00 3121616.3202
8 75.00 1827066.7118
9 5650.00 1421810.9242
10 5150.00 4116871.2277
(11 row(s) affected)
C. Using AVG with DISTINCT
This statement returns the average list price of products in the AdventureWorks2022 database. By using DISTINCT, the calculation considers only unique values.
SELECT AVG(DISTINCT ListPrice)
FROM Production.Product;
Here's the result set.
------------------------------
437.4042
(1 row(s) affected)
D. Using AVG without DISTINCT
Without DISTINCT, the AVG function finds the average list price of all products in the Product table in the AdventureWorks2022 database, including any duplicate values.
SELECT AVG(ListPrice)
FROM Production.Product;
Here's the result set.
------------------------------
438.6662
(1 row(s) affected)
E. Using the OVER clause
The following example uses the AVG function with the OVER clause, to provide a moving average of yearly sales for each territory in the Sales.SalesPerson table in the AdventureWorks2022 database. The data is partitioned by TerritoryID and logically ordered by SalesYTD. This means that the AVG function is computed for each territory based on the sales year. For TerritoryID 1, there are two rows for sales year 2005, which represent the two sales-people with sales that year. The average sales for these two rows is calculated, and then the third row representing sales for the year 2006 is included in the calculation.
SELECT BusinessEntityID, TerritoryID
,DATEPART(yy,ModifiedDate) AS SalesYear
,CONVERT(VARCHAR(20),SalesYTD,1) AS SalesYTD
,CONVERT(VARCHAR(20),AVG(SalesYTD) OVER (PARTITION BY TerritoryID
ORDER BY DATEPART(yy,ModifiedDate)
),1) AS MovingAvg
,CONVERT(VARCHAR(20),SUM(SalesYTD) OVER (PARTITION BY TerritoryID
ORDER BY DATEPART(yy,ModifiedDate)
),1) AS CumulativeTotal
FROM Sales.SalesPerson
WHERE TerritoryID IS NULL OR TerritoryID < 5
ORDER BY TerritoryID,SalesYear;
Here's the result set.
BusinessEntityID TerritoryID SalesYear SalesYTD MovingAvg CumulativeTotal
---------------- ----------- ----------- -------------------- -------------------- --------------------
274 NULL 2005 559,697.56 559,697.56 559,697.56
287 NULL 2006 519,905.93 539,801.75 1,079,603.50
285 NULL 2007 172,524.45 417,375.98 1,252,127.95
283 1 2005 1,573,012.94 1,462,795.04 2,925,590.07
280 1 2005 1,352,577.13 1,462,795.04 2,925,590.07
284 1 2006 1,576,562.20 1,500,717.42 4,502,152.27
275 2 2005 3,763,178.18 3,763,178.18 3,763,178.18
277 3 2005 3,189,418.37 3,189,418.37 3,189,418.37
276 4 2005 4,251,368.55 3,354,952.08 6,709,904.17
281 4 2005 2,458,535.62 3,354,952.08 6,709,904.17
(10 row(s) affected)
In this example, the OVER clause doesn't include PARTITION BY. This means that the function applies to all rows returned by the query. The ORDER BY clause specified in the OVER clause determines the logical order to which the AVG function applies. The query returns a moving average of sales, by year, for all sales territories specified in the WHERE clause. The ORDER BY clause specified in the SELECT statement determines the order in which the SELECT statement displays the rows of the query.
SELECT BusinessEntityID, TerritoryID
,DATEPART(yy,ModifiedDate) AS SalesYear
,CONVERT(VARCHAR(20),SalesYTD,1) AS SalesYTD
,CONVERT(VARCHAR(20),AVG(SalesYTD) OVER (ORDER BY DATEPART(yy,ModifiedDate)
),1) AS MovingAvg
,CONVERT(VARCHAR(20),SUM(SalesYTD) OVER (ORDER BY DATEPART(yy,ModifiedDate)
),1) AS CumulativeTotal
FROM Sales.SalesPerson
WHERE TerritoryID IS NULL OR TerritoryID < 5
ORDER BY SalesYear;
Here's the result set.
BusinessEntityID TerritoryID SalesYear SalesYTD MovingAvg CumulativeTotal
---------------- ----------- ----------- -------------------- -------------------- --------------------
274 NULL 2005 559,697.56 2,449,684.05 17,147,788.35
275 2 2005 3,763,178.18 2,449,684.05 17,147,788.35
276 4 2005 4,251,368.55 2,449,684.05 17,147,788.35
277 3 2005 3,189,418.37 2,449,684.05 17,147,788.35
280 1 2005 1,352,577.13 2,449,684.05 17,147,788.35
281 4 2005 2,458,535.62 2,449,684.05 17,147,788.35
283 1 2005 1,573,012.94 2,449,684.05 17,147,788.35
284 1 2006 1,576,562.20 2,138,250.72 19,244,256.47
287 NULL 2006 519,905.93 2,138,250.72 19,244,256.47
285 NULL 2007 172,524.45 1,941,678.09 19,416,780.93
(10 row(s) affected)