create javascript API that will allow web users to query my database

I need to allow partner web sites to query my database and read my online catalog. on their end they would receive a response that will allow them to update their own database. they would likely filter their request with a query filter, like a data range, and would receive back potentially a number of records. the solution needs to run on IIS at least. i need a working example of my server side code that receives the request and provides the response as well as an example of the partner sites code that would call this api, receive the response and write the data to the database.