On ons, 2002-11-13 at 16:12, 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,
Supported (ref. help in last post)

> oracle, 
Supported:http://www.cs.uwindsor.ca/meta-index/courses/95F/60-315/temp/combine.html

> ms,
Supported with EXISTS:
http://www.schemamania.org/jkl/booksonline/SQLBOL70/html/2_005_27.htm

> ibm),
Supported:
http://www-3.ibm.com/cgi-bin/db2www/data/db2/udb/winos2unix/support/document.d2w/report?fn=db2v7y0db2y040.htm


> it wouldn't be worth the work.
So, should I add a feature request?

> 
> -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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