Query with conditions that does not affect what records are shown but what an expression will return

[Nanuaraq]

I am trying to do a expression in a query that will show me one thing if a certain criteria is met, and another thing if the criteria is not met. Is this possible?

More specifically:

Assume I have a table with two columns, A and B. They are both numeric.
Values in column A are never null. There is always a number.
Values in column B may be null and may be a number.

I need an expression C:
IF the value in column B is not null, then the expression in column C must = value of column B.
ELSE IF the value in column B is null, then the expression in column C must = value of column A.

This seems like a simple enough task, but I have no idea how to go about it.



Any help would be appreciated

[pbaldy]

How about

Nz(ColumnB, ColumnA)

[davegri]

, IIf(B IS NULL,A,B) as C,

[Nanuaraq]

This works wonderfully. Thank you very much. Such a powerful tool, and yet so simple even I can understand them.
I have a lot of experimenting to do with these two babies, I think they might be very useful in other areas of my project as well. Thank you