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Re: A Not Join

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L van der Walt <mailing@xxxxxxxxxx> 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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