Transact-SQL Syntax ConventionsReturns the first value in an ordered set of values in SQL Server 2017
Transact-SQL Syntax Conventions
FIRST_VALUE ( [scalar_expression ] )
OVER ( [ partition_by_clause ] order_by_clause [ rows_range_clause ] )
scalar_expression
Is the value to be returned. scalar_expression can be a column, subquery, or other arbitrary expression that results in a single value. Other analytic functions are not permitted.
OVER ( [ partition_by_clause ] order_by_clause [ rows_range_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. rows_range_clause further limits the rows within the partition by specifying start and end points. For more information, see OVER Clause (Transact-SQL).
Is the same type as scalar_expression.
FIRST_VALUE is nondeterministic. For more information, see Deterministic and Nondeterministic Functions.
The following example uses FIRST_VALUE to return the name of the product that is the least expensive in a given product category.
USE AdventureWorks2012;
GO
SELECT Name, ListPrice,
FIRST_VALUE(Name) OVER (ORDER BY ListPrice ASC) AS LeastExpensive
FROM Production.Product
WHERE ProductSubcategoryID = 37; Here is the result set.
Name ListPrice LeastExpensive
----------------------- --------------------- --------------------
Patch Kit/8 Patches 2.29 Patch Kit/8 Patches
Road Tire Tube 3.99 Patch Kit/8 Patches
Touring Tire Tube 4.99 Patch Kit/8 Patches
Mountain Tire Tube 4.99 Patch Kit/8 Patches
LL Road Tire 21.49 Patch Kit/8 Patches
ML Road Tire 24.99 Patch Kit/8 Patches
LL Mountain Tire 24.99 Patch Kit/8 Patches
Touring Tire 28.99 Patch Kit/8 Patches
ML Mountain Tire 29.99 Patch Kit/8 Patches
HL Road Tire 32.60 Patch Kit/8 Patches
HL Mountain Tire 35.00 Patch Kit/8 Patches
The following example uses FIRST_VALUE to return the employee with the fewest number of vacation hours compared to other employees with the same job title. The PARTITION BY clause partitions the employees by job title and the FIRST_VALUE function is applied to each partition independently. The ORDER BY clause specified in the OVER clause determines the logical order in which the FIRST_VALUE function is applied to the rows in each partition. The ROWS UNBOUNDED PRECEDING clause specifies the starting point of the window is the first row of each partition.
USE AdventureWorks2012;
GO
SELECT JobTitle, LastName, VacationHours,
FIRST_VALUE(LastName) OVER (PARTITION BY JobTitle
ORDER BY VacationHours ASC
ROWS UNBOUNDED PRECEDING
) AS FewestVacationHours
FROM HumanResources.Employee AS e
INNER JOIN Person.Person AS p
ON e.BusinessEntityID = p.BusinessEntityID
ORDER BY JobTitle; Here is a partial result set.
JobTitle LastName VacationHours FewestVacationHours
----------------------------------- ------------------------- ------------- -------------------
Accountant Moreland 58 Moreland
Accountant Seamans 59 Moreland
Accounts Manager Liu 57 Liu
Accounts Payable Specialist Tomic 63 Tomic
Accounts Payable Specialist Sheperdigian 64 Tomic
Accounts Receivable Specialist Poe 60 Poe
Accounts Receivable Specialist Spoon 61 Poe
Accounts Receivable Specialist Walton 62 Poe