The VAR is an aggregate function in SQL Server which returns the variance of all or distinct values of the specified column in SQL Statement. Let's look into the syntax, Syntax SELECT VAR ( [ ALL | DISTINCT ] expression ) FROM [Table_Name] ALL - It is default. Returns the variance of all values. DISTINCT - Returns the variance of unique values ALL SELECT VAR(ALL ProductID) as ALLProduct FROM [AdventureWorks2019].[Production].[ProductInventory] The above statement returns the variance of ALL product values. DISTINCT SELECT VAR(DISTINCT ProductID) as DistinctProduct FROM [AdventureWorks2019].[Production].[ProductInventory] The above statement returns the variance of DISTINCT product values. To learn more - Click Here