Re: Matching columns in rows from two tables

On Wed, 20 Feb 2002 13:51:12 -0800
Richard Emberson <emberson@phc.net> wrote:

> I have the following tables:
>
...

> -- a group set is a set of one or more groups
> CREATE TABLE group_sets (

Group_sets is already defined, isn't it ?

>     group_id            BIGINT,
>     group_set_id        BIGINT,
>     ....
>     FOREIGN KEY (group_id) REFERENCES groups (group_id),
>     FOREIGN KEY (group_set_id) REFERENCES group_sets (group_set_id)
> );
> 
> I want to:
>     Find the group_set_id such that for a given user_id (input parameter)
>     there is a one-to-one correspondence between the group_ids associated
>     with the user_id and the group_ids associated with the group_set_id;
> 
>     for every group_id that the user_id has, the group_set_id also has it
>     and for every group_id that the group_set_id has, the user_id also has it.
>     If there is no such group_set_id, then return null.
> 
>     What query will generate the group_set_id?

I'm not sure whether or not I have understood what you described.
If I use organizations instead of the 2nd group_sets you were created,
presumably ...


-- using no joins
select org1.group_set_id from organizations as org1where exists (select org0.group_id                from organizations
asorg0               where exists (select mem.group_id                               from membership as mem
                where org0.group_id = mem.group_id                                    and user_id = <<input parameter>>
                            group by mem.group_id                             having count(*) = 1
     )                     and org1.group_id = org0.group_id               group by org0.group_id              having
count(*)= 1              )
 
;

-- using inner joins
select org2.group_set_id from (select org0.group_id          from (select group_id from membership                where
user_id= <<input parameter>>                group by group_id               having count(*) = 1              ) as mem
          inner join organizations as org0              on (mem.group_id = org0.group_id)        group by org0.group_id
     having count(*) = 1      ) as org1      inner join organizations as org2      on (org1.group_id = org2.group_id)
 
;


Regards,
Masaru Sugawara