>>What's wrong with one SP. You always can use structure like this:
>>

>>IF @Something1
>>   BEGIN
>>   -- Select 1
>>   END
>>ELSE IF @Something2
>>   BEGIN
>>   -- Select 2
>>   END
>>ELSE IF @Something3
>>   BEGIN
>>   -- Select 3
>>   END
>>

>
>That's exactly what I'm writing at the moment but I didn't know what it should be ELSE IF.
>
>BTW, I think I don't need BEGIN/END if I only have just one select command, am I right?

Correct, although personally I always enclose statements in an IF with BEGIN..END just to help readability.

>
>And I have another SQL question regarding projection. For some reason the code my colleague tried didn't work for me with the strange error.