Lets assume we have a scenario where we have to update a value in one table based on the value in another table then we can use the following:
In General we can say:

UPDATE TABLE_1 INNER JOIN TABLE_2 ON TABLE_1.COLUMN_1= TABLE_2.COLUMN_2
SET TABLE_1.COLUMN = EXPR WHERE TABLE_2.COLUMN2 = EXPR

for a particular example:

UPDATE aspnet_users au INNER JOIN aspnet_usersinroles uir ON au.username = uir.username SET email='a'  WHERE uir.rolename ='Administrator'

Hope this may help anyone