Hi Amit,
According to your requirement you need data from SQL backend and then validate it with Oracle and need to consider it as successful login, but Login to the app means registering the user with SMP, if registration (login) is successful only you will get access to backend (SQL). ie without login you can't access SQL server.
You can achieve your requirement my writing condition in the mobile app itself - After getting data from SQL server, in the background do the validation with Oracle, if it succeeds let the user go into the app else throw an error saying "No auth" and delete the registered user using the code sap.Logon.core.deleteRegistration(logonUnregisterSuccessCallback, errorCallback);
Regards, Midhun
SAP Technology RIG