How to loop through similar to a for loop - tsql

Question

I have checked the forum here and understand that t-SQL does not have FOR loops. However, I'm wondering the best way to do what I need to do here.
Here is my table (mytable) simplified:
id Code1 Code2 Code3 CodeDesc1 CodeDesc2 CodeDesk3
__ _____ _____ _____ _________ _________ _________
1 ABC DEF ZYX
2 DEF ABC ZYX
3 ZYX GHJ ABC
There are many more rows and many more Code and CodeDesc columns in the real situation. I am converting SAS code to T-SQL and the SAS code has this (simplified):
DO x = 1 to 4 ;
IF code0(x) = 'ABC' THEN CodeDesc0(x) = 'ABC Description'
ELSE
IF code0(x) = 'DEF' THEN CodeDesc0(x) = 'DEF Description'
ELSE
IF code0(x) = 'ZYX' THEN CodeDesc0(x) = 'ZYX Description'
My question is how can I do something similar in T-SQL.
Thanks for your suggestions.
Adding more info...
If I were to do what I need to do using straight T-SQL, without any programming it would look like this:
UPDATE mytable SET CodeDesc1 = 'ABC Description' WHERE Code1 = 'ABC'
UPDATE mytable SET CodeDesc2 = 'ABC Description' WHERE Code2 = 'ABC'
UPDATE mytable SET CodeDesc3 = 'ABC Description' WHERE Code3 = 'ABC'
UPDATE mytable SET CodeDesc1 = 'DEF Description' WHERE Code1 = 'DEF'
UPDATE mytable SET CodeDesc2 = 'DEF Description' WHERE Code2 = 'DEF'
UPDATE mytable SET CodeDesc3 = 'DEF Description' WHERE Code3 = 'DEF'
So, as you can see with several different codes and descriptions I could easily be writing 100's of update statements to cover all the possibilities.
I hope that helps to shed a bit more light.

Answer 1

Do not use a loop. Upddates should never be done in loops!!!!
What I would do is create a table that maps the abreviations to the long descriptions.
Then you can add new ones easily and you can write the update this way:
Update a
set description = b.description
from tableA a
join tableb b on a.abbreviation = b.abbrevation
where a.description <> b.descrioption or a.description is null

Answer 2

Here's an example of what you're looking for:
/********** example 1 **********/
declare #au_id char( 11 )
set rowcount 0
select * into #mytemp from authors
set rowcount 1
select #au_id = au_id from #mytemp
while ##rowcount <> 0
begin
set rowcount 0
select * from #mytemp where au_id = #au_id
delete #mytemp where au_id = #au_id
set rowcount 1
select #au_id = au_id from #mytemp<BR/>
end
set rowcount 0
Taken from here: http://support.microsoft.com/kb/111401