Re: Sorting by NULL values

On Tue, 2003-03-04 at 15:13, Stephan Szabo wrote:
> On Tue, 4 Mar 2003, Ian Burrell wrote:
>
> > I am doing a query where I need to sort by a column that may be NULL
> > because it is coming from an OUTER JOIN. I noticed a difference between
> > PostgreSQL and other databases about where NULLs show up. It seems that
> > with Postgres, NULLs are sorted after other values. Other databases
> > sort them before.
>
> > Is there any standard on how sorting NULLs work? Is there a way to

If you care, order by their boolean equivelent first:

order by field is null desc, field

DESC puts nulls first, since true > false

> IIRC, they're either considered greater than or less than non-NULL values,
> but the decision is up to the implementation.
>
> > change Postgres's behavior? Is there a way to replace the NULLs with
> > empty strings?
>
> Coalesce should work.
>
>
>
>
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Rod Taylor <rbt(at)rbt(dot)ca>

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