Question : How to write a conditional statement

I am working in MVS 2005. I am writing a report and I am unsure how to create a conditional statement within this module.

What I want to do is to vary what table I populate a field with dependant on specific criteria.

I have a gl transaction table that holds all of the transactions that hit our gl. When the posting is an AP transaction I want to populate the description field with the vendors name from the vendors table. When the transaction is from the AR module I want to populate the description field with the customers name from the customers table.

Example:
If gl_transactions.source_module= AP 
 gl_ gl_transactions.source_reference =venders.vendor _number

If gl_transactions.source_module= AR 
gl_ gl_transactions.source_reference =customers. customers_number

Thanks in advance!

Answer : How to write a conditional statement

just put this at the end of the select, and it will be treated as a column w/ the name of Description:

case gl_transactions.source_module
when 'AP' then vendors.vendor_number
when 'AR' then customers.customers_number
end as Description