instruction: in a year before, what is the three most frequently taken lab test for patients of 30s?
response: SELECT d_labitems.label FROM d_labitems WHERE d_labitems.itemid IN (SELECT t1.itemid FROM (SELECT labevents.itemid, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM labevents WHERE labevents.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.age BETWEEN 30 AND 39) AND DATETIME(labevents.charttime, 'start of year') = DATETIME(CURRENT_TIME(), 'start of year', '-1 year') GROUP BY labevents.itemid) AS t1 WHERE t1.c1 <= 3)