Android - How to cache Json using SQLite

Android - How to cache Json using SQLite

My application should work not only in online but also in offline mode.
When my app have internet connection, it will download data (parse from
Json) and save to SQLite database. If I turn off internet, it will get
data from SQLite to display. My problems are how I know when data update
or have new data from server. I want update current records and add new
records when data change.
Ex:
First load - Load 50 records >>> save to SQLite
Second load - Load 30 records (20 current records change & 15 new records)
Total - 65 records in SQLite
Thanks for any help