UNPIVOT Multiple Columns

Unlike PIVOT which de-normalizes the data, UNPIVOT is more helpful in getting your data back to a more normalized form.

UNPIVOT performs the opposite operation to PIVOT by rotating columns of a table-valued expression into column values.

For a single column UNPIVOT examples and for more on PIVOT and UNPIVOT you can read from Microsoft Books Online - Using PIVOT and UNPIVOT

In this article I’ll try to show you how to UNPIVOT multiple columns in a single query. There is simple trick to do that, if you are familiar with the UNPIVOT operator you will find it easy to understand.

First lets create some sample data :

-- Create sample table CREATE TABLE Suppliers (Id INT, Product VARCHAR(500), Supplier1 VARCHAR(500), Supplier2 VARCHAR(500), Supplier3 VARCHAR(500), City1 VARCHAR(500), City2 VARCHAR(500), City3 VARCHAR(500) ) GO -- Load Sample data INSERT INTO Suppliers SELECT 1, 'Car', 'Tata Motors', 'Bajaj', 'Mahindra', 'Jamshedpur','Pune','Mumbai' UNION ALL SELECT 2, 'Bike', 'Bajaj', 'Hero Honda', 'Suzuki', 'Pune', 'New Delhi', 'Chandigarh' UNION ALL SELECT 3, 'Cycle', 'Hercules', 'Hero', 'Atlas', 'Mumbai', 'Banglaore', 'Pune' GO -- Test sample data SELECT Id, Product, Supplier1, Supplier2, Supplier3, City1, City2, City3 FROM Suppliers GO

Here is how our sample table looks like :

Id	Product	Supplier1	Supplier2	Supplier3	City1	City2	City3
1	Car	TataMotors	Bajaj	Mahindra	Jamshedpur	Pune	Mumbai
2	Bike	Bajaj	Hero Honda	Suzuki	Pune	New Delhi	Chandigarh
3	Cycle	Hercules	Hero	Atlas	Mumbai	Bangalore	Pune

And as you can see here we have 2 columns which needs to be UNPIVOT, first is Supplier and second is there respective Cities.  If it was single column to be UNPIVOTed it could have been a straight forward task.  Thing is you can write a query with 2 UNPIVOT operators, but question is how to JOIN two UNPIVOT sub queries correctly so we will get the each supplier with its respective city next to it in second column?

As I said earlier there is simple trick to do that.  See the following query and its WHERE condition :

SELECT Id,     Product,     ROW_NUMBER()OVER(Partition By Id Order By Suppliers) as SuppId,     SupplierName,     CityName FROM ( SELECT Id, Product, Supplier1, Supplier2, Supplier3, City1, City2, City3 FROM Suppliers ) Main UNPIVOT ( SupplierName FOR Suppliers IN (Supplier1, Supplier2, Supplier3) ) Sup UNPIVOT ( CityName For Cities IN (City1, City2, City3) ) Ct WHERE RIGHT(Suppliers,1) =  RIGHT(Cities,1)

And here is the Output of the query :

Id	Product	SuppId	SupplierName	CityName
1	Car	1	Tata Motors	Jamshedpur
1	Car	2	Bajaj	Pune
1	Car	3	Mahindra	Mumbai
2	Bike	1	Bajaj	Pune
2	Bike	2	Hero Honda	New Delhi
2	Bike	3	Suzuki	Chandigarh
3	Cycle	1	Hercules	Mumbai
3	Cycle	2	Hero	Bangalore
3	Cycle	3	Atlas	Pune

So the trick was this where condition -

WHERE RIGHT(Suppliers,1) =  RIGHT(Cities,1)

There are other ways also to UNPIVOT the multiple columns, may be some other time I’ll post them too. 

Source of inspiration for this post is following thread on MSDN forums - http://social.msdn.microsoft.com/Forums/en-US/transactsql/thread/54626179-ee9f-4db7-a31e-c02104bdd6beAt 

At the end of it, OP also come up with his own solution he got from SQLTeam’s forums.

Mangal Pardeshi