Connect oracle database to sharepoint list

Question

Hello,
I've a requirement for my project where I'll have to
1) Establish connection between Oracle database and SharePointList
2) Populate data in SharePoint list by pulling data (Querying) from Oracle database.

http://www.c-sharpcorner.com/UploadFile/anavijai/how-to-create-wcf-service-to-retrieve-data-from-the-oracle-database/

The above is the reference link I used,
The sample example uses one table, ex: employeedetails table and methods to extract employee information
select statements I use are required to use more than one table for grabbing information. Can I get example where multiple tables are involved (joining of tables) in select statement and the corresponding C# code for the same.