instruction: until 2103, what are the five most frequently taken lab tests for patients of age 20s?
response: SELECT t1.labname FROM (SELECT lab.labname, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM lab WHERE lab.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.age BETWEEN 20 AND 29) AND STRFTIME('%y', lab.labresulttime) <= '2103' GROUP BY lab.labname) AS t1 WHERE t1.c1 <= 5