Note: This upgrade was test performed on development server with using bits of SQL Server 2012 RC0 (which was available at in public) when this test was performed. However, SQL Server RTM (GA on April 1) is expected to behave similarly.

I recently observed an upgrade from SQL Server 2005 to SQL Server 2012 with compatibility keeping at SQL Server 2012 (110). After upgrading the system and testing the various modules of the application, we quickly observed that few of the reports were not working. They were throwing error. When looked at carefully I noticed that it was using COMPUTE BY clause, which is deprecated in SQL Server 2012. COMPUTE BY clause is replaced by ROLL UP clause in SQL Server 2012. However there is no direct replacement of the code, user have to re-write quite a few things when using ROLL UP instead of COMPUTE BY. The primary reason is that how each of them returns results. In original code COMPUTE BY was resulting lots of result set but ROLL UP.

Here is the example of the similar code of ROLL UP and COMPUTE BY. I personally find the ROLL UP much easier than COMPUTE BY as it returns all the results in single resultset unlike the other one. Here is the quick code which I wrote to demonstrate the said behavior.

CREATE TABLE tblPopulation (
Country VARCHAR(100),
[State] VARCHAR(100),
City VARCHAR(100),
[Population (in Millions)] INT
)
GO
INSERT INTO tblPopulation VALUES('India', 'Delhi','East Delhi',9 )
INSERT INTO tblPopulation VALUES('India', 'Delhi','South Delhi',8 )
INSERT INTO tblPopulation VALUES('India', 'Delhi','North Delhi',5.5)
INSERT INTO tblPopulation VALUES('India', 'Delhi','West Delhi',7.5)
INSERT INTO tblPopulation VALUES('India', 'Karnataka','Bangalore',9.5)
INSERT INTO tblPopulation VALUES('India', 'Karnataka','Belur',2.5)
INSERT INTO tblPopulation VALUES('India', 'Karnataka','Manipal',1.5)
INSERT INTO tblPopulation VALUES('India', 'Maharastra','Mumbai',30)
INSERT INTO tblPopulation VALUES('India', 'Maharastra','Pune',20)
INSERT INTO tblPopulation VALUES('India', 'Maharastra','Nagpur',11 )
INSERT INTO tblPopulation VALUES('India', 'Maharastra','Nashik',6.5)
GO
SELECT Country,[State],City,
SUM ([Population (in Millions)]) AS [Population (in Millions)]
FROM tblPopulation
GROUP BY Country,[State],City
WITH ROLLUP
GO
SELECT Country,[State],City, [Population (in Millions)]
FROM tblPopulation
ORDER BY Country,[State],City
COMPUTE SUM([Population (in Millions)]) BY Country,[State]--,City
GO

After writing this blog post I continuously feel that there should be some better way to do the same task. Is there any easier way to replace COMPUTE BY?

Reference: Pinal Dave (http://blog.sqlauthority.com)

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