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SQL Server – TSQL – GROUP BY GROUPING SETS()

12.07.2011 4 comments

By using GROUPING SETS() we can specify multiple groupings in a single query. GROUPING SETS() generates the result by producing a UNION ALL set of the result sets generated by specified grouping sets.

for example, consider below data:

— © 2011 – Vishal (http://SqlAndMe.com)

 

SELECT      [Group], [Name], [SalesYTD]

FROM        dbo.Sales

Result Set:

Group                          Name                           SalesYTD

—————————— —————————— —————————————

North America                  Northwest                      123237.00

South America                  Northwest                      37534.00

South America                  Southwest                      39667.00

North America                  Southwest                      164232.00

 

(4 row(s) affected)

 

To summarize this data we can use GROUP BY, to summarize by more that one set we need multiple SELECTs, and UNION ALL to merge the result set:

SELECT      [Group], [Name], SUM(SalesYTD) AS 'Total Sales'

FROM        dbo.Sales

GROUP BY [Group], [Name]

 

UNION ALL

 

SELECT      [Group], NULL, SUM(SalesYTD) AS 'Total Sales'

FROM        dbo.Sales

GROUP BY [Group]

 

UNION ALL

 

SELECT      NULL, NULL, SUM(SalesYTD) AS 'Total Sales'

FROM        dbo.Sales

Result Set:

Group                          Name                           Total Sales

—————————— —————————— —————————————

North America                  Northwest                      123237.00

South America                  Northwest                      37534.00

North America                  Southwest                      164232.00

South America                  Southwest                      39667.00

North America                  NULL                           287469.00

South America                  NULL                           77201.00

NULL                           NULL                           364670.00

 

(7 row(s) affected)

The above result set can be achieved by a single GROUPING SETS() clause as below:

— WITH ROLLUP Equivalent

SELECT      [Group], [Name], SUM(SalesYTD) AS 'Total Sales'

FROM        dbo.Sales

GROUP BY GROUPING SETS (([Group], [Name]), ([Group]), ())

As the sets we have specified generate sub-total and a grand-total row, the same result set can be produced by using GROUP BY ROLLUP().

The empty set ‘( )’ in GROUPING SETS() generates grand total.

 

GROUPING SETS() can also be used to generate results produced by GROUP BY CUBE(), since we can specify all the sets generated by GROUP BY CUBE().

SELECT      [Group], [Name], SUM(SalesYTD) AS 'Total Sales'

FROM        dbo.Sales

GROUP BY CUBE ([Group], [Name])

 

— WITH CUBE Equivalent

SELECT      [Group], [Name], SUM(SalesYTD) AS 'Total Sales'

FROM        dbo.Sales

GROUP BY GROUPING SETS (([Group], [Name]), ([Group]), ([Name]), ())

Result Set (2nd):

Group                          Name                           Total Sales

—————————— —————————— —————————————

North America                  Northwest                      123237.00

South America                  Northwest                      37534.00

NULL                           Northwest                      160771.00

North America                  Southwest                      164232.00

South America                  Southwest                      39667.00

NULL                           Southwest                      203899.00

NULL                           NULL                           364670.00

North America                  NULL                           287469.00

South America                  NULL                           77201.00

 

(9 row(s) affected)

 

Let’s take another example, if you need to generate a pivot table based on sales data, you will need to group data by multiple sets:

Product

Year

 

 

2008

1009

2010

2011

Total

Product 1

GROUP BY (Product, Year)

GROUP BY (Product)

Product 2

Product 3

ALL

GROUP BY (Year)

GROUP BY ()

To generate this pivot, we need to group results by four different sets, This can be written using T-SQL as below:

— Equivalent to GROUP BY CUBE

SELECT      [Product], [Year], SUM(SalesYTD) AS 'Total Sales'

FROM        dbo.ProductSales

GROUP BY GROUPING SETS

(     ([Product], [Year]),

      ([Product]),

      ([Year]),

      ()

)

Hope This Helps!

Vishal