Re: A Not Join

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От stig erikson
Тема Re: A Not Join
Дата
Msg-id dlta4i$2hvu$1@news.hub.org
обсуждение исходный текст
Ответ на A Not Join  (L van der Walt <mailing@lani.co.za>)
Список pgsql-sql
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')



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