Android run code using values from records in sqlite database

I've created an android application that stores user data in an sqlite database. I was able to create the database and insert, update, and delete records without a problem. But there is one more action I need to perform using values from some records stored, and this code should run when the device first boots up. I added the android permission and created the boot class, but I can't figure out how to extract the fields from the required records and run the code on each one of the values obtained.

Basically, I need to create a query to select only the required records. Then I need to extract all the values from a certain field in the selected records. Then I need a code to run once for every value obtained.

Any help on how I can go about doing this properly would be much appreciated. Thank you.