NTILE (Transact-SQL)
Distributes the rows in an ordered partition into a specified number of groups. The groups are numbered, starting at one. For each row, NTILE returns the number of the group to which the row belongs.
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Transact-SQL Syntax Conventions
Syntax
NTILE (integer_expression) OVER ( [ <partition_by_clause> ] < order_by_clause > )
Arguments
integer_expression
Is a positive integer constant expression that specifies the number of groups into which each partition must be divided. integer_expression can be of type int, or bigint.<partition_by_clause>
Divides the result set produced by the FROM clause into partitions to which the function is applied. For the PARTITION BY syntax, see OVER Clause (Transact-SQL).<order_by_clause>
Determines the order in which the NTILE values are assigned to the rows in a partition. An integer cannot represent a column when the <order_by_clause> is used in a ranking function.
Return Types
bigint
Remarks
If the number of rows in a partition is not divisible by integer_expression, this will cause groups of two sizes that differ by one member. Larger groups come before smaller groups in the order specified by the OVER clause. For example if the total number of rows is 53 and the number of groups is five, the first three groups will have 11 rows and the two remaining groups will have 10 rows each. If on the other hand the total number of rows is divisible by the number of groups, the rows will be evenly distributed among the groups. For example, if the total number of rows is 50, and there are five groups, each bucket will contain 10 rows.
Examples
A. Dividing rows into groups
The following example divides rows into four groups of employees based on their year-to-date sales. Because the total number of rows is not divisible by the number of groups, the first two groups have four rows and the remaining groups have three rows each.
USE AdventureWorks2012;
GO
SELECT p.FirstName, p.LastName
,NTILE(4) OVER(ORDER BY SalesYTD DESC) AS Quartile
,CONVERT(nvarchar(20),s.SalesYTD,1) AS SalesYTD
, a.PostalCode
FROM Sales.SalesPerson AS s
INNER JOIN Person.Person AS p
ON s.BusinessEntityID = p.BusinessEntityID
INNER JOIN Person.Address AS a
ON a.AddressID = p.BusinessEntityID
WHERE TerritoryID IS NOT NULL
AND SalesYTD <> 0;
GO
Here is the result set.
FirstName LastName Quartile SalesYTD PostalCode
------------- --------------------- --------- -------------- ----------
Linda Mitchell 1 4,251,368.55 98027
Jae Pak 1 4,116,871.23 98055
Michael Blythe 1 3,763,178.18 98027
Jillian Carson 1 3,189,418.37 98027
Ranjit Varkey Chudukatil 2 3,121,616.32 98055
José Saraiva 2 2,604,540.72 98055
Shu Ito 2 2,458,535.62 98055
Tsvi Reiter 2 2,315,185.61 98027
Rachel Valdez 3 1,827,066.71 98055
Tete Mensa-Annan 3 1,576,562.20 98055
David Campbell 3 1,573,012.94 98055
Garrett Vargas 4 1,453,719.47 98027
Lynn Tsoflias 4 1,421,810.92 98055
Pamela Ansman-Wolfe 4 1,352,577.13 98027
(14 row(s) affected)
B. Dividing the result set by using PARTITION BY
The following example adds the PARTITION BY argument to the code in example A. The rows are first partitioned by PostalCode and then divided into four groups within each PostalCode. The example also declares a variable @NTILE\_Var and uses that variable to specify the value for the integer_expression parameter.
USE AdventureWorks2012;
GO
DECLARE @NTILE_Var int = 4;
SELECT p.FirstName, p.LastName
,NTILE(@NTILE_Var) OVER(PARTITION BY PostalCode ORDER BY SalesYTD DESC) AS Quartile
,CONVERT(nvarchar(20),s.SalesYTD,1) AS SalesYTD
,a.PostalCode
FROM Sales.SalesPerson AS s
INNER JOIN Person.Person AS p
ON s.BusinessEntityID = p.BusinessEntityID
INNER JOIN Person.Address AS a
ON a.AddressID = p.BusinessEntityID
WHERE TerritoryID IS NOT NULL
AND SalesYTD <> 0;
GO
Here is the result set.
FirstName LastName Quartile SalesYTD PostalCode
------------ -------------------- -------- ------------ ----------
Linda Mitchell 1 4,251,368.55 98027
Michael Blythe 1 3,763,178.18 98027
Jillian Carson 2 3,189,418.37 98027
Tsvi Reiter 2 2,315,185.61 98027
Garrett Vargas 3 1,453,719.47 98027
Pamela Ansman-Wolfe 4 1,352,577.13 98027
Jae Pak 1 4,116,871.23 98055
Ranjit Varkey Chudukatil 1 3,121,616.32 98055
José Saraiva 2 2,604,540.72 98055
Shu Ito 2 2,458,535.62 98055
Rachel Valdez 3 1,827,066.71 98055
Tete Mensa-Annan 3 1,576,562.20 98055
David Campbell 4 1,573,012.94 98055
Lynn Tsoflias 4 1,421,810.92 98055
(14 row(s) affected)