In Dynamics AX2012, it uses security policy(AOT->Security->Policies) to replace Record-Level security. Record-Level security will not be deprecated in the AX2012 and future version will be not supported.

So let's create a simple policy step by step.

1, Define a Query named Test1 as a record inquiry.

This inquiry will get data from sales table and sales line.

Step 1, Drag Saleline and SalesTable as the first and second data source on the Query.

Step 2, Configure Fields property as Dynamic on both SalesLine and SalesTable data source for all fields selected. 

Step 3, The property of SalesTable, fetch mode is 1:1 and relations is Yes

Step 4, The range of SalesTable node, Please select AccountNum as the field and value is a certain value.

2, Create the policy named Test2.

Step 1, Properity, Lable: Test, Primary table: SalesLine,  ConstrainedTable: Yes, Enabled: Yes, ContextType: RoleName, The select your role name in RoleName.

Step 2, Drag SalesTable on the node of constrained tables.

If the user who has this role, and he can access SalesTable Form, he'll only can see the reocords as query condition.