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SELECT - OVER clause (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 SQL database in Microsoft Fabric

The OVER clause determines the partitioning and ordering of a rowset before the associated window function is applied. That is, the OVER clause defines a window or user-specified set of rows within a query result set. A window function then computes a value for each row in the window. You can use the OVER clause with functions to compute aggregated values such as moving averages, cumulative aggregates, running totals, or top N per group results.

Transact-SQL syntax conventions

Syntax

Syntax for SQL Server, Azure SQL Database, and Azure Synapse Analytics.

OVER (
       [ <PARTITION BY clause> ]
       [ <ORDER BY clause> ]
       [ <ROW or RANGE clause> ]
      )

<PARTITION BY clause> ::=
PARTITION BY value_expression , ... [ n ]

<ORDER BY clause> ::=
ORDER BY order_by_expression
    [ COLLATE collation_name ]
    [ ASC | DESC ]
    [ , ...n ]

<ROW or RANGE clause> ::=
{ ROWS | RANGE } <window frame extent>

<window frame extent> ::=
{   <window frame preceding>
  | <window frame between>
}
<window frame between> ::=
  BETWEEN <window frame bound> AND <window frame bound>

<window frame bound> ::=
{   <window frame preceding>
  | <window frame following>
}

<window frame preceding> ::=
{
    UNBOUNDED PRECEDING
  | <unsigned_value_specification> PRECEDING
  | CURRENT ROW
}

<window frame following> ::=
{
    UNBOUNDED FOLLOWING
  | <unsigned_value_specification> FOLLOWING
  | CURRENT ROW
}

<unsigned value specification> ::=
{  <unsigned integer literal> }

Syntax for Parallel Data Warehouse.

OVER ( [ PARTITION BY value_expression ] [ order_by_clause ] )

Arguments

Window functions might have the following arguments in their OVER clause:

  • PARTITION BY that divides the query result set into partitions.

  • ORDER BY that defines the logical order of the rows within each partition of the result set.

  • ROWS or RANGE that limits the rows within the partition by specifying start and end points within the partition. It requires ORDER BY argument and the default value is from the start of partition to the current element if the ORDER BY argument is specified.

If you don't specify any argument, the window functions are applied on the entire result set.

SELECT object_id,
       MIN(object_id) OVER () AS [min],
       MAX(object_id) OVER () AS [max]
FROM sys.objects;
object_id min max
3 3 2139154666
5 3 2139154666
... ... ...
2123154609 3 2139154666
2139154666 3 2139154666

PARTITION BY

Divides the query result set into partitions. The window function is applied to each partition separately and computation restarts for each partition.

PARTITION BY <value_expression>

If PARTITION BY isn't specified, the function treats all rows of the query result set as a single partition.

The function is applied on all rows in the partition if you don't specify ORDER BY clause.

PARTITION BY value_expression

Specifies the column by which the rowset is partitioned. value_expression can only refer to columns made available by the FROM clause. value_expression can't refer to expressions or aliases in the select list. value_expression can be a column expression, scalar subquery, scalar function, or user-defined variable.

SELECT object_id,
       type,
       MIN(object_id) OVER (PARTITION BY type) AS [min],
       MAX(object_id) OVER (PARTITION BY type) AS [max]
FROM sys.objects;
object_id type min max
68195293 PK 68195293 711673583
631673298 PK 68195293 711673583
711673583 PK 68195293 711673583
... ... ... ...
3 S 3 98
5 S 3 98
... ... ... ...
98 S 3 98
... ... ... ...

ORDER BY

ORDER BY <order_by_expression> [ COLLATE <collation_name> ] [ ASC | DESC ]

Defines the logical order of the rows within each partition of the result set. That is, it specifies the logical order in which the window function calculation is performed.

  • If not specified, the default order is ASC and the window function uses all rows in the partition.

  • If specified, and a ROWS or RANGE isn't specified, then default RANGE UNBOUNDED PRECEDING AND CURRENT ROW is used as the default for the window frame, by the functions that can accept an optional ROWS or RANGE specification (for example, min or max).

SELECT object_id,
       type,
       MIN(object_id) OVER (PARTITION BY type ORDER BY object_id) AS [min],
       MAX(object_id) OVER (PARTITION BY type ORDER BY object_id) AS [max]
FROM sys.objects;
object_id type min max
68195293 PK 68195293 68195293
631673298 PK 68195293 631673298
711673583 PK 68195293 711673583
... ... ...
3 S 3 3
5 S 3 5
6 S 3 6
... ... ...
97 S 3 97
98 S 3 98
... ... ...

order_by_expression

Specifies a column or expression on which to sort. order_by_expression can only refer to columns made available by the FROM clause. An integer can't be specified to represent a column name or alias.

COLLATE collation_name

Specifies that the ORDER BY operation should be performed according to the collation specified in collation_name. collation_name can be either a Windows collation name or a SQL collation name. For more information, see Collation and Unicode support. COLLATE is applicable only for columns of type char, varchar, nchar, and nvarchar.

ASC | DESC

Specifies that the values in the specified column should be sorted in ascending or descending order. ASC is the default sort order. Null values are treated as the lowest possible values.

ROWS or RANGE

Applies to: SQL Server 2012 (11.x) and later versions.

Further limits the rows within the partition by specifying start and end points within the partition. It specifies a range of rows with respect to the current row either by logical association or physical association. Physical association is achieved by using the ROWS clause.

The ROWS clause limits the rows within a partition by specifying a fixed number of rows preceding or following the current row. Alternatively, the RANGE clause logically limits the rows within a partition by specifying a range of values with respect to the value in the current row. Preceding and following rows are defined based on the ordering in the ORDER BY clause. The window frame RANGE ... CURRENT ROW ... includes all rows that have the same values in the ORDER BY expression as the current row. For example, ROWS BETWEEN 2 PRECEDING AND CURRENT ROW means that the window of rows that the function operates on is three rows in size, starting with 2 rows preceding until and including the current row.

SELECT object_id,
       COUNT(*) OVER (ORDER BY object_id ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS [preceding],
       COUNT(*) OVER (ORDER BY object_id ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING) AS [central],
       COUNT(*) OVER (ORDER BY object_id ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) AS [following]
FROM sys.objects
ORDER BY object_id ASC;
object_id preceding central following
3 1 3 156
5 2 4 155
6 3 5 154
7 4 5 153
8 5 5 152
... ... ... ...
2112726579 153 5 4
2119678599 154 5 3
2123154609 155 4 2
2139154666 156 3 1

ROWS or RANGE requires that you specify the ORDER BY clause. If ORDER BY contains multiple order expressions, CURRENT ROW FOR RANGE considers all columns in the ORDER BY list when determining the current row.

UNBOUNDED PRECEDING

Applies to: SQL Server 2012 (11.x) and later versions.

Specifies that the window starts at the first row of the partition. UNBOUNDED PRECEDING can only be specified as window starting point.

<unsigned value specification> PRECEDING

Specified with <unsigned value specification> to indicate the number of rows or values to precede the current row. This specification isn't allowed for RANGE.

CURRENT ROW

Applies to: SQL Server 2012 (11.x) and later versions.

Specifies that the window starts or ends at the current row when used with ROWS or the current value when used with RANGE. CURRENT ROW can be specified as both a starting and ending point.

BETWEEN AND

Applies to: SQL Server 2012 (11.x) and later versions.

BETWEEN <window frame bound> AND <window frame bound>

Used with either ROWS or RANGE to specify the lower (starting) and upper (ending) boundary points of the window. <window frame bound> defines the boundary starting point and <window frame bound> defines the boundary endpoint. The upper bound can't be smaller than the lower bound.

UNBOUNDED FOLLOWING

Applies to: SQL Server 2012 (11.x) and later versions.

Specifies that the window ends at the last row of the partition. UNBOUNDED FOLLOWING can only be specified as a window endpoint. For example, RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING defines a window that starts with the current row and ends with the last row of the partition.

<unsigned value specification> FOLLOWING

Specified with <unsigned value specification> to indicate the number of rows or values to follow the current row. When <unsigned value specification> FOLLOWING is specified as the window starting point, the ending point must be <unsigned value specification> FOLLOWING. For example, ROWS BETWEEN 2 FOLLOWING AND 10 FOLLOWING defines a window that starts with the second row that follows the current row and ends with the tenth row that follows the current row. This specification isn't allowed for RANGE.

<unsigned integer literal>

Applies to: SQL Server 2012 (11.x) and later versions.

A positive integer literal (including 0) that specifies the number of rows or values to precede or follow the current row or value. This specification is valid only for ROWS.

Remarks

More than one window function can be used in a single query with a single FROM clause. The OVER clause for each function can differ in partitioning and ordering.

If PARTITION BY isn't specified, the function treats all rows of the query result set as a single group.

Important

If ROWS or RANGE is specified and <window frame preceding> is used for <window frame extent> (short syntax) then this specification is used for the window frame boundary starting point and CURRENT ROW is used for the boundary ending point. For example, ROWS 5 PRECEDING is equal to ROWS BETWEEN 5 PRECEDING AND CURRENT ROW.

If ORDER BY isn't specified, the entire partition is used for a window frame. This applies only to functions that don't require ORDER BY clause. If ROWS or RANGE isn't specified but ORDER BY is specified, RANGE UNBOUNDED PRECEDING AND CURRENT ROW is used as default for window frame. This applies only to functions that have can accept optional ROWS or RANGE specification. For example, ranking functions can't accept ROWS or RANGE, therefore this window frame isn't applied even though ORDER BY is present and ROWS or RANGE is not.

Limitations

The OVER clause can't be used with the DISTINCT aggregations.

RANGE can't be used with <unsigned value specification> PRECEDING or <unsigned value specification> FOLLOWING.

Depending on the ranking, aggregate, or analytic function used with the OVER clause, <ORDER BY clause> and/or the <ROWS and RANGE clause> might not be supported.

Examples

The Transact-SQL code samples in this article use the AdventureWorks2022 or AdventureWorksDW2022 sample database, which you can download from the Microsoft SQL Server Samples and Community Projects home page.

A. Use the OVER clause with the ROW_NUMBER function

The following example shows using the OVER clause with ROW_NUMBER function to display a row number for each row within a partition. The ORDER BY clause specified in the OVER clause orders the rows in each partition by the column SalesYTD. The ORDER BY clause in the SELECT statement determines the order in which the entire query result set is returned.

USE AdventureWorks2022;
GO

SELECT ROW_NUMBER() OVER (PARTITION BY PostalCode ORDER BY SalesYTD DESC) AS "Row Number",
       p.LastName,
       s.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
ORDER BY PostalCode;
GO

Here's the result set.

Row Number      LastName                SalesYTD              PostalCode
--------------- ----------------------- --------------------- ----------
1               Mitchell                4251368.5497          98027
2               Blythe                  3763178.1787          98027
3               Carson                  3189418.3662          98027
4               Reiter                  2315185.611           98027
5               Vargas                  1453719.4653          98027
6               Ansman-Wolfe            1352577.1325          98027
1               Pak                     4116871.2277          98055
2               Varkey Chudukatil       3121616.3202          98055
3               Saraiva                 2604540.7172          98055
4               Ito                     2458535.6169          98055
5               Valdez                  1827066.7118          98055
6               Mensa-Annan             1576562.1966          98055
7               Campbell                1573012.9383          98055
8               Tsoflias                1421810.9242          98055

B. Use the OVER clause with aggregate functions

The following example uses the OVER clause with aggregate functions over all rows returned by the query. In this example, using the OVER clause is more efficient than using subqueries to derive the aggregate values.

USE AdventureWorks2022;
GO

SELECT SalesOrderID,
       ProductID,
       OrderQty,
       SUM(OrderQty) OVER (PARTITION BY SalesOrderID) AS Total,
       AVG(OrderQty) OVER (PARTITION BY SalesOrderID) AS "Avg",
       COUNT(OrderQty) OVER (PARTITION BY SalesOrderID) AS "Count",
       MIN(OrderQty) OVER (PARTITION BY SalesOrderID) AS "Min",
       MAX(OrderQty) OVER (PARTITION BY SalesOrderID) AS "Max"
FROM Sales.SalesOrderDetail
WHERE SalesOrderID IN (43659, 43664);
GO

Here's the result set.

SalesOrderID ProductID   OrderQty Total       Avg         Count       Min    Max
------------ ----------- -------- ----------- ----------- ----------- ------ ------
43659        776         1        26          2           12          1      6
43659        777         3        26          2           12          1      6
43659        778         1        26          2           12          1      6
43659        771         1        26          2           12          1      6
43659        772         1        26          2           12          1      6
43659        773         2        26          2           12          1      6
43659        774         1        26          2           12          1      6
43659        714         3        26          2           12          1      6
43659        716         1        26          2           12          1      6
43659        709         6        26          2           12          1      6
43659        712         2        26          2           12          1      6
43659        711         4        26          2           12          1      6
43664        772         1        14          1           8           1      4
43664        775         4        14          1           8           1      4
43664        714         1        14          1           8           1      4
43664        716         1        14          1           8           1      4
43664        777         2        14          1           8           1      4
43664        771         3        14          1           8           1      4
43664        773         1        14          1           8           1      4
43664        778         1        14          1           8           1      4

The following example shows using the OVER clause with an aggregate function in a calculated value.

USE AdventureWorks2022;
GO

SELECT SalesOrderID,
       ProductID,
       OrderQty,
       SUM(OrderQty) OVER (PARTITION BY SalesOrderID) AS Total,
       CAST (1. * OrderQty / SUM(OrderQty) OVER (PARTITION BY SalesOrderID) * 100 AS DECIMAL (5, 2)) AS [Percent by ProductID]
FROM Sales.SalesOrderDetail
WHERE SalesOrderID IN (43659, 43664);
GO

Here's the result set. The aggregates are calculated by SalesOrderID and the Percent by ProductID is calculated for each line of each SalesOrderID.

SalesOrderID ProductID   OrderQty Total       Percent by ProductID
------------ ----------- -------- ----------- ---------------------------------------
43659        776         1        26          3.85
43659        777         3        26          11.54
43659        778         1        26          3.85
43659        771         1        26          3.85
43659        772         1        26          3.85
43659        773         2        26          7.69
43659        774         1        26          3.85
43659        714         3        26          11.54
43659        716         1        26          3.85
43659        709         6        26          23.08
43659        712         2        26          7.69
43659        711         4        26          15.38
43664        772         1        14          7.14
43664        775         4        14          28.57
43664        714         1        14          7.14
43664        716         1        14          7.14
43664        777         2        14          14.29
43664        771         3        14          21.4
43664        773         1        14          7.14
43664        778         1        14          7.14

C. Produce a moving average and cumulative total

The following example uses the AVG and SUM functions with the OVER clause to provide a moving average and cumulative total of yearly sales for each territory in the Sales.SalesPerson table. 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 of 1, there are two rows for sales year 2005 representing the two sales people with sales that year. The average sales for these two rows are computed, and then the third row representing sales for the year 2006 is included in the computation.

USE AdventureWorks2022;
GO

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

In this example, the OVER clause doesn't include PARTITION BY. This means that the function is applied 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 is applied. 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 rows of the query are displayed.

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

D. Specify the ROWS clause

Applies to: SQL Server 2012 (11.x) and later versions.

The following example uses the ROWS clause to define a window over which the rows are computed as the current row and the N number of rows that follow (one row in this example).

SELECT BusinessEntityID,
       TerritoryID,
       CONVERT (VARCHAR (20), SalesYTD, 1) AS SalesYTD,
       DATEPART(yy, ModifiedDate) AS SalesYear,
       CONVERT (VARCHAR (20), SUM(SalesYTD) OVER (PARTITION BY TerritoryID ORDER BY DATEPART(yy, ModifiedDate) ROWS BETWEEN CURRENT ROW AND 1 FOLLOWING), 1) AS CumulativeTotal
FROM Sales.SalesPerson
WHERE TerritoryID IS NULL
      OR TerritoryID < 5;

Here's the result set.

BusinessEntityID TerritoryID SalesYTD             SalesYear   CumulativeTotal
---------------- ----------- -------------------- ----------- --------------------
274              NULL        559,697.56           2005        1,079,603.50
287              NULL        519,905.93           2006        692,430.38
285              NULL        172,524.45           2007        172,524.45
283              1           1,573,012.94         2005        2,925,590.07
280              1           1,352,577.13         2005        2,929,139.33
284              1           1,576,562.20         2006        1,576,562.20
275              2           3,763,178.18         2005        3,763,178.18
277              3           3,189,418.37         2005        3,189,418.37
276              4           4,251,368.55         2005        6,709,904.17
281              4           2,458,535.62         2005        2,458,535.62

In the following example, the ROWS clause is specified with UNBOUNDED PRECEDING. The result is that the window starts at the first row of the partition.

SELECT BusinessEntityID,
       TerritoryID,
       CONVERT (VARCHAR (20), SalesYTD, 1) AS SalesYTD,
       DATEPART(yy, ModifiedDate) AS SalesYear,
       CONVERT (VARCHAR (20), SUM(SalesYTD) OVER (PARTITION BY TerritoryID ORDER BY DATEPART(yy, ModifiedDate) ROWS UNBOUNDED PRECEDING), 1) AS CumulativeTotal
FROM Sales.SalesPerson
WHERE TerritoryID IS NULL
      OR TerritoryID < 5;

Here's the result set.

BusinessEntityID TerritoryID SalesYTD             SalesYear   CumulativeTotal
---------------- ----------- -------------------- ----------- --------------------
274              NULL        559,697.56           2005        559,697.56
287              NULL        519,905.93           2006        1,079,603.50
285              NULL        172,524.45           2007        1,252,127.95
283              1           1,573,012.94         2005        1,573,012.94
280              1           1,352,577.13         2005        2,925,590.07
284              1           1,576,562.20         2006        4,502,152.27
275              2           3,763,178.18         2005        3,763,178.18
277              3           3,189,418.37         2005        3,189,418.37
276              4           4,251,368.55         2005        4,251,368.55
281              4           2,458,535.62         2005        6,709,904.17

Examples: Analytics Platform System (PDW)

E. Use the OVER clause with the ROW_NUMBER function

The following example returns the ROW_NUMBER for sales representatives based on their assigned sales quota.

SELECT ROW_NUMBER() OVER (ORDER BY SUM(SalesAmountQuota) DESC) AS RowNumber,
       FirstName,
       LastName,
       CONVERT (VARCHAR (13), SUM(SalesAmountQuota), 1) AS SalesQuota
FROM dbo.DimEmployee AS e
     INNER JOIN dbo.FactSalesQuota AS sq
         ON e.EmployeeKey = sq.EmployeeKey
WHERE e.SalesPersonFlag = 1
GROUP BY LastName, FirstName;

Here's a partial result set.

RowNumber  FirstName  LastName            SalesQuota
---------  ---------  ------------------  -------------
1          Jillian    Carson              12,198,000.00
2          Linda      Mitchell            11,786,000.00
3          Michael    Blythe              11,162,000.00
4          Jae        Pak                 10,514,000.00

F. Use the OVER clause with aggregate functions

The following examples show using the OVER clause with aggregate functions. In this example, using the OVER clause is more efficient than using subqueries.

SELECT SalesOrderNumber AS OrderNumber,
       ProductKey,
       OrderQuantity AS Qty,
       SUM(OrderQuantity) OVER (PARTITION BY SalesOrderNumber) AS Total,
       AVG(OrderQuantity) OVER (PARTITION BY SalesOrderNumber) AS AVG,
       COUNT(OrderQuantity) OVER (PARTITION BY SalesOrderNumber) AS COUNT,
       MIN(OrderQuantity) OVER (PARTITION BY SalesOrderNumber) AS MIN,
       MAX(OrderQuantity) OVER (PARTITION BY SalesOrderNumber) AS MAX
FROM dbo.FactResellerSales
WHERE SalesOrderNumber IN (N'SO43659', N'SO43664')
      AND ProductKey LIKE '2%'
ORDER BY SalesOrderNumber, ProductKey;

Here's the result set.

OrderNumber  Product  Qty  Total  Avg  Count  Min  Max
-----------  -------  ---  -----  ---  -----  ---  ---
SO43659      218      6    16     3    5      1    6
SO43659      220      4    16     3    5      1    6
SO43659      223      2    16     3    5      1    6
SO43659      229      3    16     3    5      1    6
SO43659      235      1    16     3    5      1    6
SO43664      229      1     2     1    2      1    1
SO43664      235      1     2     1    2      1    1

The following example shows using the OVER clause with an aggregate function in a calculated value. The aggregates are calculated by SalesOrderNumber and the percentage of the total sales order is calculated for each line of each SalesOrderNumber.

SELECT SalesOrderNumber AS OrderNumber,
       ProductKey AS Product,
       OrderQuantity AS Qty,
       SUM(OrderQuantity) OVER (PARTITION BY SalesOrderNumber) AS Total,
       CAST (1. * OrderQuantity / SUM(OrderQuantity) OVER (PARTITION BY SalesOrderNumber) * 100 AS DECIMAL (5, 2)) AS PctByProduct
FROM dbo.FactResellerSales
WHERE SalesOrderNumber IN (N'SO43659', N'SO43664')
      AND ProductKey LIKE '2%'
ORDER BY SalesOrderNumber, ProductKey;

The first start of this result set is as follows:

OrderNumber  Product  Qty  Total  PctByProduct
-----------  -------  ---  -----  ------------
SO43659      218      6    16     37.50
SO43659      220      4    16     25.00
SO43659      223      2    16     12.50
SO43659      229      2    16     18.75