sql server update colA based on value in colB

I have to update a column in a table based on the value of another column in the same table.  

col A holds the varchar value of a number
col B is the range of that number

if col A = '30' then col B needs to be updated to '30-40'
if col A = '50' then col B needs to be updated to '50-100'

please help.
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

SharathData EngineerCommented:
How do you determine the ranges? Do you want a range of gap 10 or 50? What are all possible ranges you are looking for?
Scott PletcherSenior DBACommented:
You'd be far better off with colB as a computed column, since you wouldn't have to UPDATE when colA changed:

ALTER TABLE dbo.tablename
    WHEN colA LIKE '3[0-9]' OR colA = '40' THEN '30-40'
    WHEN colA LIKE '[56789][0-9]' OR colA = '100' THEN '50-100'

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Microsoft SQL Server 2008

From novice to tech pro — start learning today.