July 07, 2010

Find Maximum Value in each Row – SQL Server

Here’s a simple and efficient way to find the maximum value in each row using SQL Server UNPIVOT

DECLARE @t table (id int PRIMARY KEY, col1 int, col2 int, col3 int)

-- SAMPLE DATA
INSERT INTO @t SELECT 1, 45, 2, 14
INSERT INTO @t SELECT 2, 8, 1, 12
INSERT INTO @t SELECT 3, 21, 20, 8
INSERT INTO @t SELECT 4, 8, 5, 2
INSERT INTO @t SELECT 5, 23, 49, 7
INSERT INTO @t SELECT 6, 19, 7, 5
INSERT INTO @t SELECT 7, 7, 7, 2
INSERT INTO @t SELECT 8, 14, 17, 2

-- QUERY
SELECT id, MAX(col) AS maxValue
FROM
(
SELECT id, col FROM @t
UNPIVOT
(col FOR ListofColumns IN (col1,col2,col3))
AS unpivott) AS p
GROUP BY id


OUTPUT

image


If you new to UNPIVOT, read Using PIVOT and UNPIVOT


About The Author

Suprotim Agarwal, ASP.NET Architecture MVP works as an Architect Consultant and provides consultancy on how to design and develop Web applications.

Suprotim is also the founder and primary contributor to DevCurry, DotNetCurry and SQLServerCurry. He has also written an EBook 51 Recipes using jQuery with ASP.NET Controls.

Follow him on twitter @suprotimagarwal

7 comments:

D. Taylor said...

Simply brilliant. Can i find the highest and lowest value using any other approach than UNPIVOT. If you have the time, I just need this example for my knowledge

Madhivanan said...

Taylor,

Try this method

select id, min(col1) as minValue, max(col1) as maxValue from
(
select id, col1 from @t
union all
select id, col2 from @t
union all
select id, col3 from @t
) as t
group by id

If you use version 2008, you can use values clause, refer point 3 in this post
http://beyondrelational.com/blogs/madhivanan/archive/2010/08/02/values-clause-in-sql-server-2008.aspx

Suprotim Agarwal said...

Thanks Madhivanan. I too had written a query yesterday in response to this comment where I used CROSS APPLY. The advantage was using this, the OP can update existing columns if there's a need.

http://www.sqlservercurry.com/2011/02/sql-server-highest-and-lowest-values-in.html

Gopal said...

Excellent, great, useful.. Saved my 5 days effort and frustration..

Awesome thinking, efficient method.

Thanks so so so much :)

SQLGeek said...

My question is to Madhivanan:
First of all thanks for the solution given above.
But adding to the above question if id column is not given, then how will we do it

Unknown said...
This comment has been removed by the author.
madhivanan said...

SQLGeek, if you do not have id column, you can use CASE expression

select
case
when col1>col2 and col1>col3 then col1
when col2>col3 then col2
else col3
end as maximum_value
from table