Re: AW: Re: [SQL] behavior of ' = NULL' vs. MySQL vs. Stand ards

"Joe Conway" <joseph(dot)conway(at)home(dot)com> writes:
> I also noticed that in PostgreSQL I can do the following (both before and
> after this patch):
> select f2 is null from foo;
> whereas in both Oracle and MSSQL it causes a syntax error. Any thoughts on
> this?

I dug into this further and discovered that indeed it is not SQL92
... but it is SQL99. Amazingly enough, SQL92 doesn't allow boolean
expressions as a possible type of general expression:

<value expression> ::=
<numeric value expression>
| <string value expression>
| <datetime value expression>
| <interval value expression>

It only allows them as <search condition>s, which is to say WHERE,
HAVING, CASE WHEN, CHECK, and one or two other places.

But SQL99 gets it right:

<value expression> ::=
<numeric value expression>
| <string value expression>
| <datetime value expression>
| <interval value expression>
| <boolean value expression>
| <user-defined type value expression>
| <row value expression>
| <reference value expression>
| <collection value expression>

Looks like we're ahead of the curve here...

regards, tom lane