Thread: Complex query help please

Complex query help please

From

"Glenn MacGregor"

Date:

27 November 2001, 20:24:33

Hi All,

I am new to sql and have the need for a complex query. I have figured out how to do it in two queries but I would like to get it down to one. I will give you my queries and hopefully some can give me some assistance.

Thanks

Query 1:

create temp table ttable1 as select xpressuser.username, xpressvimpermission.commandaccess, xpressvimpermission.eventaccess from xpressvim left join xpressvimpermission using (vimid) left join xpressgroup using (groupid) left join xpressuser using (groupid) where xpressvim.vimname = 'testvim2';

creates a temp table.

Query 2:

select * from ttable1 union select xpressuser.username, xpressgroup.commandaccess, xpressgroup.eventaccess from xpressgroup left join xpressuser using (groupid) where xpressuser.username not in (select username from ttable1) and (xpressgroup.commandaccess != 'n' or xpressgroup.eventaccess != 'f');

So the idea is I have a default set of permissions that users get, these permissions can be overridden on each vim for each group(user). The first query results in a table which has all the overridden permissions.

The second query results in a table which has all the default permissions unioned with the previous table and not in the previous table.

Is there any way to do this one query or a function?

Thanks

Glenn

Re: Complex query help please

From

"Josh Berkus"

Date:

27 November 2001, 22:33:53

Glenn,

> I am new to sql and have the need for a complex query.  I have
> figured out how to do it in two queries but I would like to get it
> down to one.  I will give you my queries and hopefully some can give
> me some assistance.
> Thanks

Easy.  Take your second query, and everywhere you have "ttable1" replace
it with a sub-select which is the first query.  Thus:

Query 1:
create temp table ttable1 as select xpressuser.username,
xpressvimpermission.commandaccess, xpressvimpermission.eventaccess from
xpressvim left join xpressvimpermission using (vimid) left join
xpressgroup using (groupid) left join xpressuser using (groupid) where
xpressvim.vimname = 'testvim2';
creates a temp table.

select xpressuser.username, xpressvimpermission.commandaccess,
xpressvimpermission.eventaccess from xpressvim left join
xpressvimpermission using (vimid) left join xpressgroup using (groupid)
left join xpressuser using (groupid) where xpressvim.vimname =
'testvim2'
union select xpressuser.username, xpressgroup.commandaccess,
xpressgroup.eventaccess from xpressgroup left join xpressuser using
(groupid) where xpressuser.username not in (select xpressuser.username
from xpressvim left join xpressvimpermission using (vimid) left join
xpressgroup using (groupid) left join xpressuser using (groupid) where
xpressvim.vimname = 'testvim2') and (xpressgroup.commandaccess != 'n' or
xpressgroup.eventaccess != 'f');

You can play with different query structures (WHERE NOT EXISTS, etc) for
performance reasons.  Certainly you should save the above as a view to
get optimization.

ALso, make sure that you're using Postgres 7.1.0 or above.

-Josh

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