Abstract: Systems and processes for assembling de-identified patient healthcare data records in a longitudinal database are provided. The systems and processes may be implemented over multiple data suppliers and common database facilities while ensuring patient privacy. At the data supplier locations, patient-identifying attributes in the data records are placed in standard format and then doubly encrypted using a pair of encryption keys before transmission to a common database facility. The pair of encryption keys includes a key specific to the data supplier and a key specific to the common database facility. At the common database facility, the encryption specific to the data supplier is removed, so that multi-sourced data records have only the common database encryption. Without direct access to patient identifying-information, the encrypted data records are assigned dummy labels or tags by which the data records can be longitudinally linked in the database.