Hi Martijn, Helen and Lucas,

thanks for your answers and recommendations.
The way you all explained it made sense to me.

In this case, my problem was related to IBExpert because
as a result to a select which returns no row, IBExpert
shows "<null>". So I thought that in my SP, the result would
be NULL if no row was found.
IBExpert is great, but sometimes it pollutes the "purity"
of FB ;-)
Anyway, I should have known that.

A little question concerning your suggestions concerning colons
before local variables: in some cases, the use of colons is not
enforced, that means that you are able to use the local variable
without a preceeding colon.

Is it only bad practice to do this or does it also have
other negative implications?


Christian