instruction: retrieve patient ids of patients who are diagnosed with cerebral subdural hematoma - secondary to trauma until 4 years ago.
response: SELECT patient.uniquepid FROM patient WHERE patient.patientunitstayid IN (SELECT diagnosis.patientunitstayid FROM diagnosis WHERE diagnosis.diagnosisname = 'cerebral subdural hematoma - secondary to trauma' AND DATETIME(diagnosis.diagnosistime) <= DATETIME(CURRENT_TIME(), '-4 year'))