Re: Sorting by an arbitrary criterion

On Thu, Jul 9, 2009 at 6:26 PM, Craig James<craig_james@emolecules.com> wrote:
> Suppose I have a large table with a small-cardinality CATEGORY column (say,
> categories 1..5).  I need to sort by an arbitrary (i.e. user-specified)
> mapping of CATEGORY, something like this:
>
>  1 => 'z'
>  2 => 'a'
>  3 => 'b'
>  4 => 'w'
>  5 => 'h'
>
> So when I get done, the sort order should be 2,3,5,4,1.

If the object is to avoid a separate table, you can do it with a
"case" statement:

  select ... from ...
  order by case category
    when 1 then 'z'
    when 2 then 'a'
    when 3 then 'b'
    when 4 then 'w'
    when 5 then 'h'
  end

If you this sounds slow, you're right. But it might perform well
enough for your use case.

A.