You need to provide a solution to provide the sales managers with the required access.

Create a security role that has a table filter on the Sales_Manager table where

username = UserName()

Create a security role that has a table filter on the Region_Manager table where

sales_manager_id = UserPrincipalName().

Create a security role that has a table filter on the Sales_Manager table where

name = UserName().

Create a security role that has a table filter on the Sales_Manager table where

username = sales_manager_id.