InfoPath Dev

Dear All,
I want to create a form with one main list and one sub-list (Repeating table).
When We select a Job Number from the top drop-down-list, data will retrieve from List1 and List2.
See the attached image link http://imgur.com/a/aFMpg Click here

I have tried this tutorial
Unfortunately, Sandbox has been deprecated in SharePoint Online. So it is not possible to add custom codes (C#/VB) anymore.

I am kindly requesting you to send me a clear tutorial link which has explained about Sharepoint Parent-Child Lists Add/Update/Delete
Thank you,
Supun Silva

This is just not going to be possible in SharePoint Online with InfoPath. Perhaps investigate PowerApps? See if it may have the functionality you need?

I should add - FormsViewer incorporates qRules commands that can do this - check out FormsViewer here: http://www.qdabra.com/en/product/FormsViewer.aspx