>>>Sergey's solution is much simpler. Thanks anyway.
>>>
>>It is for the particular case. But I'm not 100% sure it's the correct one.
>>
>>How would the SQL determine the width of the column for UDF? With the suggested solution it leaves a room for ambiguity.
>
>Either the UDF must itself ensure a fixed width (padr() for character data), or the SQL expression must do something similar. In my case, my function already ensured a fixed width.
>
>>Also what if UDF returns values of different types?
>
>I usually avoid this kind of design, but in that case, an iif() would have to be used in the SQL expression.

That' good you put the precautions in place. If UDF would mess up, I'm not sure how SQL would work. Most probably it will return syntax error.

Anyway, I showed a generic solution for the field types which can not be easily constructed in SQL.