I am still not clear what the parameter is, but I will assume it is something like [1, 2, 3].
This is the logic you want:
If the input has numbers
return whether the field is in the array or not
Which would translate to
if count({?parameter}) > 0 then // contains at least one value
{table.field} in {?parameter}
Originally posted by lockwelle
I don't know what split does when you don't tell it the characters to split on.
By default, the delimiter for the split function is a single space.