Thread: Complex view question

----- Original Message -----

From: Glenn MacGregor

To: pgsql-sql@postgresql.org

Sent: Wednesday, January 16, 2002 2:43 PM

Subject: [SQL] Complex view question

Hi All...again,

 

I have this complex query with a union and a not in subselect.

 

Query:

select xpressvim.vimname, xpressvimpermission.commandaccess, xpressvimpermission.eventaccess from xpressvim left join xpressvimpermission using (vimid) left join xpressgroup using (groupid) left join xpressuser using (groupid) where (xpressvimpermission.commandaccess is not null and xpressuser.username = 'gtm@jabber.oracom.com') union select xpressvim.vimname, xpressgroup.commandaccess, xpressgroup.eventaccess from xpressgroup left join xpressuser using (groupid) natural join xpressvim where xpressuser.username = 'gtm@jabber.oracom.com' and xpressgroup.commandaccess != 'n' and xpressvim.vimname not in (select xpressvim.vimname from xpressvim left join xpressvimpermission using (vimid) left join xpressgroup using (groupid) left join xpressuser using (groupid) where (xpressvimpermission.commandaccess is not null and xpressuser.username = 'gtm@jabber.oracom.com'));

 

I want to make that a view where I can change the username = '' to whatever user I need it to be.  So I do the following:

create view tmpview as select xpressvim.vimname, xpressvimpermission.commandaccess, xpressvimpermission.eventaccess, xpressuser.username from xpressvim left join xpressvimpermission using (vimid) left join xpressgroup using (groupid) left join xpressuser using (groupid) union select xpressvim.vimname, xpressgroup.commandaccess, xpressgroup.eventaccess, xpressuser.username from xpressgroup left join xpressuser using (groupid) natural join xpressvim where xpressvim.vimname not in (select xpressvim.vimname from xpressvim left join xpressvimpermission using (vimid) left join xpressgroup using (groupid) left join xpressuser using (groupid));

remove all the where's except for the not in.  If I now select from the view:  select * from tmpview where mailto:username='gtm@jabber.oracom.com'  I get results but it is not the same number of rows as the other one.  The first one has the correct number of rows, the view doesn't.  Did I miss something here?

 

Thanks

        Glenn

Glenn,

First, I think that you would find your own queries easier to debug if you usedsome indenting and line breaks to
organizethe text.  Whenever I run into aquery problem, that's what I do and frequently the missed clause or
problemaggregatebecomes obvious.
 

> Query 1:  returns correct number of rows
> select * from overperms where username='test' union select * from
>  defaultperms where username='test' and vimname not in (select vimname from
>  overperms where username='test');
> 
> Query 2:  return incorrect number of rows
> create view perms as select * from overperms union select * from defaultperms
>  where vimname not in (select vimname from overperms);
> 
> select * from perms where username='test';

These two are NOT the same query, so it's unsurprising that the counts come outdifferent.  In the second query, you are
excludingALL rows present inoverperms from the count of defaultperms, not just those rows with a usernameof 'test'.
Thus,if vimname <-> username parings are variable, you willindeed get different counts for the first query than the
second.

Also, I don't think that your query structure is optimal.  I think you'remaking this harder than it needs to be.
However,I can't tell without seeingyour data structure.
 

-Josh Berkus

______AGLIO DATABASE SOLUTIONS___________________________                                      Josh Berkus Complete
informationtechnology      josh@agliodbs.com  and data management solutions       (415) 565-7293 for law firms, small
businesses       fax 621-2533   and non-profit organizations.      San Francisco
 

So is there a way to do query 1  with a view?

The query is not optimized, I want to get it working first.
   Thanks
           Glenn
----- Original Message -----
From: "Josh Berkus" <josh@agliodbs.com>
To: "Glenn MacGregor" <gtm@oracom.com>; "Glenn MacGregor" <gtm@oracom.com>;
<pgsql-sql@postgresql.org>
Sent: Wednesday, January 16, 2002 4:27 PM
Subject: Re: [SQL] Complex view question


> Glenn,
>
> First, I think that you would find your own queries easier to debug if you
used
>  some indenting and line breaks to organize the text.  Whenever I run into
a
>  query problem, that's what I do and frequently the missed clause or
problem
>  aggregate becomes obvious.
>
> > Query 1:  returns correct number of rows
> > select * from overperms where username='test' union select * from
> >  defaultperms where username='test' and vimname not in (select vimname
from
> >  overperms where username='test');
> >
> > Query 2:  return incorrect number of rows
> > create view perms as select * from overperms union select * from
defaultperms
> >  where vimname not in (select vimname from overperms);
> >
> > select * from perms where username='test';
>
> These two are NOT the same query, so it's unsurprising that the counts
come out
>  different.  In the second query, you are excluding ALL rows present in
>  overperms from the count of defaultperms, not just those rows with a
username
>  of 'test'.   Thus, if vimname <-> username parings are variable, you will
>  indeed get different counts for the first query than the second.
>
> Also, I don't think that your query structure is optimal.  I think you're
>  making this harder than it needs to be.  However, I can't tell without
seeing
>  your data structure.
>
> -Josh Berkus
>
> ______AGLIO DATABASE SOLUTIONS___________________________
>                                        Josh Berkus
>   Complete information technology      josh@agliodbs.com
>    and data management solutions       (415) 565-7293
>   for law firms, small businesses        fax 621-2533
>     and non-profit organizations.      San Francisco
>
> ---------------------------(end of broadcast)---------------------------
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>

Glenn,

> So is there a way to do query 1  with a view?
> 
> The query is not optimized, I want to get it working first.

Data structure, please.  I can't tell what we're working with here.

Also, a statement of what you want the result of the view to be would behelpful.

Finally, it may not be possible to do exactly what you want with a view, inwhich case you'll need to use a straight
query.

-Josh Berkus


______AGLIO DATABASE SOLUTIONS___________________________                                      Josh Berkus Complete
informationtechnology      josh@agliodbs.com  and data management solutions       (415) 565-7293 for law firms, small
businesses       fax 621-2533   and non-profit organizations.      San Francisco