Thanks for your answers. I tried your solution but that doesnot make any difference. The problem are the panes in Studio: when I use the criteria pane the IIF-function gives an error.
When I am building a view in scripting mode everything works fine, when I am only using the sql-pane I get an error ('=' nog recognized) but the query runs.
So I used the following code and in scripting mode it works OK:
The advantage over CASE is that the IIF uses only one column.
Thanks for your advise.