A Not Join

On Tue, Nov 01, 2005 at 04:27:01PM +0200, L van der Walt wrote:

I have three table:
Users - Contains username, ID etc...
Permissions - A permission name and ID
Link up table - The user.id and permission.id

If a user.id and a permission.id row exists in the linkuptable the user
have that permission granted.

With the statement below I can see the permissions a user have.

SELECT users.username, permissions.name
FROM users INNER JOIN linkuptable
ON (users.id = linkuptable.userid)
INNER JOIN permissions
ON (permissions.id = linkuptable.permissionid)
WHERE users.username = 'DummyUser'

How do I see the permissions that user DON'T have with a fast SQL statement.

Thus, a NOT the statement for the above SQL statement

LEFT JOIN permissions ON (...)
WHERE permissions.id IS NULL

You might have to do the NULL check in a HAVING clause instead... try
it.

BTW, this is probably better asked on pgsql-sql.
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L van der Walt <mailing@lani.co.za> writes:

I have three table:
Users - Contains username, ID etc...
Permissions - A permission name and ID
Link up table - The user.id and permission.id

If a user.id and a permission.id row exists in the linkuptable the user
have that permission granted.

With the statement below I can see the permissions a user have.

SELECT users.username, permissions.name
FROM users INNER JOIN linkuptable
ON (users.id = linkuptable.userid)
INNER JOIN permissions
ON (permissions.id = linkuptable.permissionid)
WHERE users.username = 'DummyUser'

How do I see the permissions that user DON'T have with a fast SQL statement.

Simple.

select permname
from permissions
where permid not in (
select permid
from linkage
where userid = 'dummy'
);

Or... a slick way to get the anti-permission for the whole bunch of
users is to;

cross join the userids with permids and then EXCEPT SELECT from
linkage table to filter out the active permissions.

Have fun!

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305 321-1144 (mobile http://www.JerrySievers.com/

L van der Walt wrote:

I have three table:
Users - Contains username, ID etc...
Permissions - A permission name and ID
Link up table - The user.id and permission.id

If a user.id and a permission.id row exists in the linkuptable the user
have that permission granted.

With the statement below I can see the permissions a user have.

SELECT users.username, permissions.name
FROM users INNER JOIN linkuptable
ON (users.id = linkuptable.userid)
INNER JOIN permissions
ON (permissions.id = linkuptable.permissionid)
WHERE users.username = 'DummyUser'

How do I see the permissions that user DON'T have with a fast SQL
statement.

Thus, a NOT the statement for the above SQL statement

Regards

Lani

what you need to do is select all possible permissions and then remove the
permissions that exist. try somthing like:

SELECT permissions.name
FROM permissions.name
WHERE permission.permissionid NOT IN
( SELECT permissions.permissionid
FROM users INNER JOIN linkuptable
ON (users.id = linkuptable.userid)
INNER JOIN permissions
ON (permissions.id = linkuptable.permissionid)
WHERE users.username = 'DummyUser'
)