Add column to external list

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SharePoint2010

I have 2 Tables, Division & Department with Parent Child relation. DivisionId is foreign key in Department.
I have created External content types for these 2 tables with an Association in Department Content type in SP Designer and then External lists in a SP Site.
How to display Division Name instead of Division Id in Department external list.

additional information copied from comment below
I have created all CRUD operations of Division and Department using Web services. Then created External content types using the web service. Even then i dont get the Division name in Department list.
I dont want to change my database design and want to only put Divsion id in Department Table