Обсуждение: date_part vs extract

I wonder about the difference between date_part('week', ...) and
extract(week from ...) not only but also from a performance point of
view. I read extract is standard and date_part is not. Backwards
compatibility maybe justifies the existence of date_part. Whats else?

Markus Bertheau

On 29 Nov 2001 at 09:45 (+0100), Markus Bertheau wrote:
| I wonder about the difference between date_part('week', ...) and
| extract(week from ...) not only but also from a performance point of
| view. I read extract is standard and date_part is not. Backwards
| compatibility maybe justifies the existence of date_part. Whats else?

The EXTRACT syntax ends up as a call to the internal date_part(...) 
function.  If SQL-portability is not a concern, calling date_part()
directly should be a bit quicker.

cheers. brent


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Markus Bertheau writes:

> I wonder about the difference between date_part('week', ...) and
> extract(week from ...) not only but also from a performance point of
> view. I read extract is standard and date_part is not. Backwards
> compatibility maybe justifies the existence of date_part. Whats else?

I think date_part() was adapted from Ingres.  Btw., note that the "week"
parameter (and most others) aren't standard either.

-- 
Peter Eisentraut   peter_e@gmx.net

> Markus Bertheau writes:
> 
> > I wonder about the difference between date_part('week', ...) and
> > extract(week from ...) not only but also from a performance point of
> > view. I read extract is standard and date_part is not. Backwards
> > compatibility maybe justifies the existence of date_part. Whats else?
> 
> I think date_part() was adapted from Ingres.  Btw., note that the "week"
> parameter (and most others) aren't standard either.

Yes, from Ingres.  I think Thomas added it.  Both he and I have Ingres
experience.

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