Question

I’m having some issues with a many to many relationship with a simple ACL module I’m developing.

I have three tables:

Groups

• *id_group
• name

Permissions

• *id_permission
• name

RelPermissionsGroup

• *id_relation
• group
• permission

So I had this query

SELECT * FROM acl_groups 
LEFT OUTER JOIN acl_RelPermissionsGroup 
  ON acl_groups.id_group = acl_RelPermissionsGroup.group 
LEFT OUTER JOIN acl_permissions 
  ON acl_permissions.id_permission = acl_RelPermissionsGroup.permission 
WHERE id_group > 0

If I do the query in phpmyadmin it shows fine. So, it shows all groups whether they have permissions or not and if they have it also shows them.

I see one problem here and it is that the name attribute is repeated. How can I alias every single field?
But that’s not the problem.

The problem is that doing mysqli_fetch_assoc performs fine except for the group that doesn’t have any permissions. This is what outputs:

    Array ( 
[id_group] => 2 
[name] => 
[id_relation] => 
[group] => 
[permission] => 
[id_permission] => 
)

The group ID is fine but given the fact that fields are duplicated it overrides them. Also, id_group and id_permission seems to be duplicated with group and permission respectively.

What should I do?

Answer 1

You will have to name the fields explicitly, like so

SELECT
  ag.name as group_name
  ,ap.name as permission_name
  ,ar.`group` as permission_group_id 
FROM acl_groups ag 
LEFT OUTER JOIN acl_RelPermissionsGroup ar ON ag.id_group = ar.`group` 
LEFT OUTER JOIN acl_permissions ap ON ap.id_permission = ar.permission 
WHERE id_group > 0

Don’t forget that group is a reserved word and needs to be quoted in backticks `group` like so.