my app requires getting data from a customer's database into mine and manipulating it. The challenge is different customers have their data in different databases (Oracle, mysql, DB2, sqlserver,etc) and in different formats(schema's). For each customer, I need to create a mapping of the schema elements between the customer database and mine.

I am imagining some kind of a visual tool to show the two databases metadata side by side and allow you to define the mapping manually -- but I am not sure if such a tool exists.

Have a couple of questions -
1. What approach would you take to address the above problem?
2. Are you aware of any tools which would help me in this process?

Thanks in advance,