Script to Screen Table for Duplicates

I need a script to screen my data table for duplicate records based off of the unique id. On page load, script screens new data inserted in one table and checks if any of those unique ids already exist in other tables in DB. If ids exist in DB, modal window drops from above and provides the user 3 options: 1. Overwrite aka Update with new data 2. Keep old data instead 3. Merge aka overwrite old data with new data and insert new values into old values if NULL 1 & 2 would work by a status field.