instruction: what are the five most frequent diagnoses of patients with age 30s in this year?
response: SELECT t1.diagnosisname FROM (SELECT diagnosis.diagnosisname, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM diagnosis WHERE diagnosis.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.age BETWEEN 30 AND 39) AND DATETIME(diagnosis.diagnosistime, 'start of year') = DATETIME(CURRENT_TIME(), 'start of year', '-0 year') GROUP BY diagnosis.diagnosisname) AS t1 WHERE t1.c1 <= 5