Question: What is the difference between average glucose reading for patients in the 20s and 50s?
SQL: SELECT SUM(CASE WHEN ROUND((strftime('%J', T2.DATE) - strftime('%J', T1.birthdate)) / 365) BETWEEN 20 AND 30 THEN T2.VALUE ELSE 0 END) / COUNT(CASE WHEN ROUND((strftime('%J', T2.DATE) - strftime('%J', T1.birthdate)) / 365) BETWEEN 20 AND 30 THEN T2.PATIENT END) - SUM(CASE WHEN ROUND((strftime('%J', T2.DATE) - strftime('%J', T1.birthdate)) / 365) BETWEEN 50 AND 60 THEN T2.VALUE ELSE 0 END) / COUNT(CASE WHEN ROUND((strftime('%J', T2.DATE) - strftime('%J', T1.birthdate)) / 365) BETWEEN 50 AND 60 THEN T2.PATIENT END) AS difference FROM patients AS T1 INNER JOIN observations AS T2 ON T1.patient = T2.PATIENT WHERE T2.DESCRIPTION = 'Glucose'