Suitable UX for diffing data from two diffrent table

I have a requirement to create report merging web application. Users will be able to upload 2 identical reports, and they should be able to see the differences, and select the data from which report they will use to generate a final integrated document.

I am planning to store data from both report into database tables (each has its own table) before displaying on the UI.

I am looking for a UX/UI solution/idea to display the differences, and an option for user to select data from which report, and there is a possibility that user will be able to modify the value.

Tech stacks that we will use: Spring Boot, Thymeleaf + JS + jQuery, Bootstrap, Hibernate

Please advice..

Regards, Hendry