On Sat, Aug 27, 2011 at 17:33, Arthur Fuller <fuller.artful@stripped> wrote:
> I agree 110%. It is completely pointless to index a column with that amount
> of NULLs. In practical fact I would go further: what is the point of a
> NULLable column? I try to design my tables such that every column is NOT
> NULL. In practice this is not realistic, but I try to adhere to this
> principle whenever I can. For example, it's possible to add a new Hire while
> not yet having determined which department s/he will work in, and hence
> which manager s/he will report to, but typically I deal with such scenarios
> by creating an "Undetermined" value in the corresponding lookup table.
maybe this should be a new thread, but...
what's the difference between defining a null value (ie, Undetermined
in your example is the same to you as null)? it would seem that this
would take up more space and take longer to process since null is a
built in (not-)value.
how does null effect an index? i had always assumed that, since there
is nothing there, that record wouldn't go into the index hence
wouldn't be processed when utilizing the index.