VARP (Transact-SQL)

Άρθρο
09/03/2024

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

Returns the statistical variance for the population for all values in the specified expression.

Transact-SQL syntax conventions

Syntax

-- Aggregate Function Syntax   
VARP ( [ ALL | DISTINCT ] expression )  
  
-- Analytic Function Syntax  
VARP ([ ALL ] expression) OVER ( [ partition_by_clause ] order_by_clause)

Arguments

ALL
Applies the function to all values. ALL is the default.

DISTINCT
Specifies that each unique value is considered.

expression
Is an expression of the exact numeric or approximate numeric data type category, except for the bit data type. Aggregate functions and subqueries are not 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. order_by_clause determines the logical order in which the operation is performed. order_by_clause is required. For more information, see OVER Clause (Transact-SQL).

Return Types

float

Remarks

If VARP is used on all items in a SELECT statement, each value in the result set is included in the calculation. VARP can be used with numeric columns only. Null values are ignored.

VARP is a deterministic function when used without the OVER and ORDER BY clauses. It is nondeterministic when specified with the OVER and ORDER BY clauses. For more information, see Deterministic and Nondeterministic Functions.

Examples

A: Using VARP

The following example returns the variance for the population for all bonus values in the SalesPerson table in the AdventureWorks2022 database.

SELECT VARP(Bonus)  
FROM Sales.SalesPerson;  
GO

Examples: Azure Synapse Analytics and Analytics Platform System (PDW)

B: Using VARP

The following example returns the VARPof the sales quota values in the table dbo.FactSalesQuota. The first column contains the variance of all distinct values and the second column contains the variance of all values including any duplicates values.

-- Uses AdventureWorks  
  
SELECT VARP(DISTINCT SalesAmountQuota)AS Distinct_Values, VARP(SalesAmountQuota) AS All_Values  
FROM dbo.FactSalesQuota;

Here's the result set.

Distinct_Values   All_Values
----------------  ----------------
158146830494.18   157788848582.94

C. Using VARP with OVER

The following example returns the VARP of the sales quota values for each quarter in a calendar year. Notice that the ORDER BY in the OVER clause orders the statistical variance and the ORDER BY of the SELECT statement orders the result set.

-- Uses AdventureWorks  
  
SELECT CalendarYear AS Year, CalendarQuarter AS Quarter, SalesAmountQuota AS SalesQuota,  
       VARP(SalesAmountQuota) OVER (ORDER BY CalendarYear, CalendarQuarter) AS Variance  
FROM dbo.FactSalesQuota  
WHERE EmployeeKey = 272 AND CalendarYear = 2002  
ORDER BY CalendarQuarter;