How can I return records from one table that are not found in another table based on two fields comparison ? Lets say I have 2 tables with the same structure:

table1
iIpoId int
cUserName nvarchar(25)


table2
iIpoId int
cUserName nvarchar(25)


I just wants to see records from table1 that are not in table2 based on both iIpoId and cUserName.

Sorry, brain freeze.
Daniel