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Generate combinations of data from columns.

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How can you generate various combinations of data from existing columns? This method shows one approach using the CUBE operator with the SELECT statement.

Click here to copy the following block
create table #Test (TestId   int   not NULL,
          DateEntered datetime not NULL,
          Data    char(1) not NULL,
          Seq int not NULL CHECK( Seq BETWEEN 1 And 10 )
);

insert into #Test values (1, '2000-08-17', 'A' , 1);
insert into #Test values (1, '2000-08-17', 'B' , 2);
insert into #Test values (1, '2000-08-17', 'C' , 3);
insert into #Test values (1, '2000-08-17', 'D' , 4);
insert into #Test values (1, '2000-08-17', 'E' , 5);

insert into #Test values (2, '2000-08-17', 'A' , 1);
insert into #Test values (2, '2000-08-17', 'C' , 2);
insert into #Test values (2, '2000-08-17', 'E' , 3);

SELECT * FROM #Test;
/*
TestId   DateEntered       Data Seq    
----------- ------------------------------------------------------ ---- -----------
     1 2000-08-17 00:00:00.000 A       1
     1 2000-08-17 00:00:00.000 B       2
     1 2000-08-17 00:00:00.000 C       3
     1 2000-08-17 00:00:00.000 D       4
     1 2000-08-17 00:00:00.000 E       5
     2 2000-08-17 00:00:00.000 A       1
     2 2000-08-17 00:00:00.000 C       2
     2 2000-08-17 00:00:00.000 E       3
*/

go
-- Objective:
-- To generate all possible combinations of the values in the data column for each test.
-- Consider the 3 values for Test = 2 i.e., A / C / E
-- The required combinations are:
-- A / C / E / AC / AE / CE / ACE

-- The SELECT statement below demonstrates a trick using the CUBE operator in SQL Server
-- The CUBE operator generates combinations of data in the grouped columns & the summaries.
-- We use this property to solve the problem:
SELECT DISTINCT *
FROM (
SELECT MIN( t2.TestID ) AS TestID , MIN( t2.DateEntered ) AS DateEntered ,
    t2.D1 , t2.D2 , t2.D3 , t2.D4 , t2.D5
FROM (
SELECT t1.TestID , t1.DateEntered ,
    MIN( CASE t1.Seq WHEN 1 THEN t1.Data END ) AS d1 ,
    MIN( CASE t1.Seq WHEN 2 THEN t1.Data END ) AS d2 ,
    MIN( CASE t1.Seq WHEN 3 THEN t1.Data END ) AS d3 ,
    MIN( CASE t1.Seq WHEN 4 THEN t1.Data END ) AS d4 ,
    MIN( CASE t1.Seq WHEN 5 THEN t1.Data END ) AS d5
FROM #Test AS t1
GROUP BY t1.TestID , t1.DateEntered
) AS t2
GROUP BY t2.D1 , t2.D2 , t2.D3 , t2.D4 , t2.D5
WITH CUBE
) AS t3
WHERE COALESCE( t3.D1 , t3.D2 , t3.D3 , t3.D4 , t3.D5 ) IS NOT NULL;

-- Output of the derived table aliased as T1
-- This is a simple cross-tab of the data using the Seq column.
/*
TestID DateEntered       d1  d2  d3  d4  d5 
------ ----------------------- ---- ---- ---- ---- ----
   1 2000-08-17 00:00:00.000 A  B  C  D  E
   2 2000-08-17 00:00:00.000 A  C  E  NULL NULL
*/


-- Output of the next derived table using the CUBE operator &
-- grouping on d1 , d2 , d3 , d4 & d5. Shown only for 2 because of
-- of the explosion of the rows when using CUBE. See BOL for more details.
/*
    As you can see from the output , we have got the combinations
    that we wanted + some extra rows because of the super summaries
    generated by the CUBE operator. These rows has NULL for columns
    d1 , d2 , d3 , d4 & d5. Typically you would use GROUPING to determine
    which is an actual NULL data & which one is the summary row. For our
    example , the aggregate function that we used is a simple MIN & we can
    just eliminate all these NULL values. This is achieved finally by using
    the DISTINCT query with the COALESCE where clause.
*/

/*
TestID   DateEntered       D1  D2  D3  D4  D5 
----------- ------------------------ ---- ---- ---- ---- ----
     2 2000-08-17 00:00:00.000 NULL NULL NULL NULL NULL
     2 2000-08-17 00:00:00.000 NULL NULL NULL NULL NULL
     2 2000-08-17 00:00:00.000 NULL NULL NULL NULL NULL
     2 2000-08-17 00:00:00.000 NULL NULL E  NULL NULL
     2 2000-08-17 00:00:00.000 NULL NULL E  NULL NULL
     2 2000-08-17 00:00:00.000 NULL NULL E  NULL NULL
     2 2000-08-17 00:00:00.000 NULL NULL E  NULL NULL
     2 2000-08-17 00:00:00.000 NULL C  NULL NULL NULL
     2 2000-08-17 00:00:00.000 NULL C  NULL NULL NULL
     2 2000-08-17 00:00:00.000 NULL C  NULL NULL NULL
     2 2000-08-17 00:00:00.000 NULL C  NULL NULL NULL
     2 2000-08-17 00:00:00.000 NULL C  E  NULL NULL
     2 2000-08-17 00:00:00.000 NULL C  E  NULL NULL
     2 2000-08-17 00:00:00.000 NULL C  E  NULL NULL
     2 2000-08-17 00:00:00.000 NULL C  E  NULL NULL
     2 2000-08-17 00:00:00.000 A  NULL NULL NULL NULL
     2 2000-08-17 00:00:00.000 A  NULL NULL NULL NULL
     2 2000-08-17 00:00:00.000 A  NULL NULL NULL NULL
     2 2000-08-17 00:00:00.000 A  NULL E  NULL NULL
     2 2000-08-17 00:00:00.000 A  NULL E  NULL NULL
     2 2000-08-17 00:00:00.000 A  NULL E  NULL NULL
     2 2000-08-17 00:00:00.000 A  NULL E  NULL NULL
     2 2000-08-17 00:00:00.000 A  C  NULL NULL NULL
     2 2000-08-17 00:00:00.000 A  C  NULL NULL NULL
     2 2000-08-17 00:00:00.000 A  C  NULL NULL NULL
     2 2000-08-17 00:00:00.000 A  C  NULL NULL NULL
     2 2000-08-17 00:00:00.000 A  C  E  NULL NULL
     2 2000-08-17 00:00:00.000 A  C  E  NULL NULL
     2 2000-08-17 00:00:00.000 A  C  E  NULL NULL
     2 2000-08-17 00:00:00.000 A  C  E  NULL NULL
*/



-- Final output ( shown for TestID = 2 only ):
/*
TestID   DateEntered       D1  D2  D3  D4  D5 
----------- ------------------------ ---- ---- ---- ---- ----
     2 2000-08-17 00:00:00.000 NULL NULL E  NULL NULL
     2 2000-08-17 00:00:00.000 NULL C  NULL NULL NULL
     2 2000-08-17 00:00:00.000 NULL C  E  NULL NULL
     2 2000-08-17 00:00:00.000 A  NULL NULL NULL NULL
     2 2000-08-17 00:00:00.000 A  NULL E  NULL NULL
     2 2000-08-17 00:00:00.000 A  C  NULL NULL NULL
     2 2000-08-17 00:00:00.000 A  C  E  NULL NULL
*/


Submitted By : Nayan Patel  (Member Since : 5/26/2004 12:23:06 PM)

Job Description : He is the moderator of this site and currently working as an independent consultant. He works with VB.net/ASP.net, SQL Server and other MS technologies. He is MCSD.net, MCDBA and MCSE. In his free time he likes to watch funny movies and doing oil painting.
View all (893) submissions by this author  (Birth Date : 7/14/1981 )


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