Custom Reports with Approver Information

We need to create custom reports whereby approver details are required, as in who approved the request. We are able to fetch out requester details like who requested, when was request generated etc, but unable to get the approval details in schema. Behind every request, a multi-level workflow runs and we need to fetch out the approver details with respect to each request

Please provide table details which hold approver details and the mapping between request_key and approver_key, so that we can track the approvers for each request.