Use left outer join and left OUTER join in Access database when querying user's permissions

The most common view is to make the left outer connection. and its role, especially when we query the user's current permissions is particularly obvious, we will be the permissions table is the module table put → role permissions table → role table → user role table → user table so that the left outer join connection, so that the user's permissions can be queried.

The left outer connection in the Access database is very special, it is first written inside and then gradually expanded to the end, first executed inside.

Example

SELECT Xt_user. Pkid, Xt_user. UserID, Xt_user. UserName, Xt_user. Password, Xt_user. Status, Xt_module. ModuleName
From (((Xt_module left JOIN xt_rolemodule on Xt_module. Pkid = Xt_rolemodule. Modulepkid) left JOIN xt_role on Xt_role. Pkid = Xt_rolemodule. Rolepkid) left JOIN xt_userrole on Xt_role. Pkid = Xt_userrole. Rolepkid) left JOIN xt_user on Xt_user. Pkid=xt_userrole. Userpkid;

Use left outer join and left OUTER join in Access database when querying user's permissions