Don't know who supports it, but it is standard sql-92 (intermed level, not
entry)
david jencks
On 2002.11.13 10:12:35 -0500 Dain Sundstrom wrote:
> That shouldn't be to hard once we add support for sub queries, but
> unless it is supported by most of the major vendors (postgres, oracle,
> ms, ibm), it wouldn't be worth the work.
>
> -dain
>
> [EMAIL PROTECTED] wrote:
> > On Tue, Nov 12, 2002 at 04:53:28PM -0600, Dain Sundstrom wrote:
> >
> >>What is an INTERSECTION query?
> >
> >>From postgresql-help:
> >
> > Syntax:
> > SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]
> > * | expression [ AS output_name ] [, ...]
> > [ FROM from_item [, ...] ]
> > [ WHERE condition ]
> > [ GROUP BY expression [, ...] ]
> > [ HAVING condition [, ...] ]
> > *** [ { UNION | INTERSECT | EXCEPT [ ALL ] } select ] ***
> > [ ORDER BY expression [ ASC | DESC | USING operator ] [, ...] ]
> > [ FOR UPDATE [ OF tablename [, ...] ] ]
> > [ LIMIT { count | ALL } [ { OFFSET | , } start ]]
> >
> > I think it is used like:
> > SELECT personID from persondata where datatype=1 AND value="ln1"
> > INTERSECT
> > SELECT personID from persondata where datatype=2 AND value="ln2"
> >
> > finds the persons registered with ln1 as datatype 1 and ln2 as datatype
> 2.
> >
> > I think the obvious solution "SELECT personID from persondata where
> (datatype=1 AND value=ln1") AND (datatype=2 AND value="ln2") doesn't
> work, as it compares one and one row.
> >
> > In this table, personID isn't unique.
> >
> >
> >> Is it widely supported?
> >
> > I suppose so in the major DBs, if it isn't a simpler solution to this
> problem (using just one SQL statement).
> >
> > In addition UNION and EXCEPT should be implemented (if these are not
> possible to work around).
>
>
>
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