| From: | "Kevin Grittner" <kgrittn(at)mail(dot)com> |
|---|---|
| To: | "David Johnston" <polobo(at)yahoo(dot)com>,"Adrian Klaver" <adrian(dot)klaver(at)gmail(dot)com>,"jg" <jg(at)rilk(dot)com> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Coalesce bug ? |
| Date: | 2012-12-21 16:24:08 |
| Message-ID: | 20121221162408.144640@gmx.com |
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| Thread: | |
| Lists: | pgsql-general |
David Johnston wrote:
> I thought that in order to call the Coalesce function the system
> would have to know the value of all parameters. There is no lazy
> instantiation in SQL.
Tom already addressed the main question, but I want to clarify this
point. COALESCE is not a function; it is defined by the standard as
a short form of a CASE statement. The syntax just makes it look
similar to a function. As a CASE statement, it stops when it finds
the right (non-NULL) case.
-Kevin
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