Cross-Tab Reports
Sometimes it is necessary to rotate results so that columns are presented horizontally and rows are presented vertically. This is known as creating a PivotTable®, creating a cross-tab report, or rotating data.
Assume there is a table Pivot that has one row per quarter. A
SELECT of Pivot reports the quarters vertically:
Year Quarter Amount
---- ------- ------
1990 1 1.1
1990 2 1.2
1990 3 1.3
1990 4 1.4
1991 1 2.1
1991 2 2.2
1991 3 2.3
1991 4 2.4
A report must be produced with a table that contains one row for each year, with the values for each quarter appearing in a separate column, such as:
Year
Q1
Q2
Q3
Q4
1990
1.1
1.2
1.3
1.4
1991
2.1
2.2
2.3
2.4
These are the statements used to create the Pivot table and populate it with the data from the first table:
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USE Northwind
GO
CREATE TABLE Pivot
( Year SMALLINT,
Quarter TINYINT,
Amount DECIMAL( 2 , 1 ) )
GO
INSERT INTO Pivot VALUES ( 1990 , 1 , 1 . 1 )
INSERT INTO Pivot VALUES ( 1990 , 2 , 1 . 2 )
INSERT INTO Pivot VALUES ( 1990 , 3 , 1 . 3 )
INSERT INTO Pivot VALUES ( 1990 , 4 , 1 . 4 )
INSERT INTO Pivot VALUES ( 1991 , 1 , 2 . 1 )
INSERT INTO Pivot VALUES ( 1991 , 2 , 2 . 2 )
INSERT INTO Pivot VALUES ( 1991 , 3 , 2 . 3 )
INSERT INTO Pivot VALUES ( 1991 , 4 , 2 . 4 )
GO
This is the
SELECT statement used to create the rotated results:
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SELECT Year,
SUM(CASE Quarter WHEN 1 THEN Amount ELSE 0 END) AS Q1,
SUM(CASE Quarter WHEN 2 THEN Amount ELSE 0 END) AS Q2,
SUM(CASE Quarter WHEN 3 THEN Amount ELSE 0 END) AS Q3,
SUM(CASE Quarter WHEN 4 THEN Amount ELSE 0 END) AS Q4
FROM Northwind.dbo.Pivot
GROUP BY Year
GO
This
SELECT statement also handles a table in which there are multiple rows for each quarter. The
GROUP BY combines all rows in Pivot for a given year into a single row in the output. When the grouping operation is being performed, the
CASE functions in the
SUM aggregates are applied in such a way that the Amount values for each quarter are added into the proper column in the result set and 0 is added to the result set columns for the other quarters.
If the results of this
SELECT statement are used as input to a spreadsheet, it is easy for the spreadsheet to calculate a total for each year. When the
SELECT is used from an application it may be easier to enhance the
SELECT statement to calculate the yearly total. For example:
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SELECT P1.*, (P1.Q1 + P1.Q2 + P1.Q3 + P1.Q4) AS YearTotal
FROM (SELECT Year,
SUM(CASE P.Quarter WHEN 1 THEN P.Amount ELSE 0 END) AS Q1,
SUM(CASE P.Quarter WHEN 2 THEN P.Amount ELSE 0 END) AS Q2,
SUM(CASE P.Quarter WHEN 3 THEN P.Amount ELSE 0 END) AS Q3,
SUM(CASE P.Quarter WHEN 4 THEN P.Amount ELSE 0 END) AS Q4
FROM Pivot AS P
GROUP BY P.Year) AS P1
GO
Both
GROUP BY with
CUBE and
GROUP BY with
ROLLUP compute the same sort of information as shown in the example, but in a slightly different format.
