Getting the exact edited data from a column in SQL Server
There's a solution for SQL Server. You can create triggers for tracking these changes, tables where the old and new values will be stored and when a trigger is fired, insert the old and new values into the storage tables

You can also use a tool that will track the changes, I use ApexSQL Audit  - doesn't actually store both versions of the complete table, but stores old and new values for the modified column, so you can recreate the old versions. As it stores all changes in database tables, so I've created some custom reports

And to answer your questions directly


  Are there any necessary changes in the tables?


Yes, triggers are added


  What is the query for getting exact edited data of the artContents column?


It doesn't show just the modified characters, but the old and the new column values