Method and system for data privacy protection in relational databases

A computing system for protecting private attributes of multiple data entities stored in a relational database, comprising

• at least one processor and at least one memory communicatively coupled to the at least one processor, the memory including computer-readable instructions that when executed by the at least one processor cause the computing system to implement steps comprising:
• storing non-private attributes of a data entity in respective non-private attribute fields of a non-private record of a non-private table, wherein an entity type of the data entity is one of multiple entity types stored in the relational database, wherein the non-private table is one of multiple non-private tables identified according to corresponding entity types, and wherein each non-private record of each of the non-private tables includes a record identifier field and at least one non-private attribute field;
• storing private attributes of the data entity in private attribute fields of private records of a private table, wherein each record of the private table includes a single private-attribute field and a key field, wherein the key field is a transformation of an entity type, a record identifier, and an attribute identifier, wherein the entity type identifies the non-private table storing the non-private attributes of the data entity, the record identifier identifies the non-private record storing the non-private attributes of the data entity, and the attribute identifier indicates a type of the private attribute is stored in the private attribute field;
• and
• retrieving a private attribute of the data entity by performing a query including a join function of the private table and the non-private table storing the non-private attributes of the data entity, wherein retrieving the private attribute comprises retrieving a private record storing the private attribute, and wherein the key field of the retrieved private record is a transformation of the entity type of the data entity, of the record identifier of the data entity, and of an attribute type of the retrieved private attribute.