Described herein is a system that processes personal data in databases. The system samples data stored in columns of data tables and analyzes the sampled data to determine whether the sampled data includes personal data. Based on the analysis, the system marks which data tables and which columns of the data tables store personal data. The system receives a request to process personal data for a subject. From data tables that are marked as storing personal data, the system identifies records storing personal data for the subject. The system additionally identifies other data tables marked as storing personal data that reference or are referenced by the data tables including the records referencing the subject. The system processes the data stored in the columns that are marked as storing personal data.