I tried. But the IsNull in Load is not usable in such scenario.
Because, by using ISNULL in the Table with masterCode, there won't be any difference. The reason is that, in the Table with MasterCode, the records is perfect (all with value). But the problem lies in another table having more records than the one table with masterCode.
Creating extra field? Mm...still thinking how will it help and how to do it. Thanks for the reply.