Question: Complaint about Credit Card mostly came from clients of which age group?
SQL: SELECT SUM(CASE WHEN T1.age > 13 AND T1.age <= 19 THEN 1 ELSE 0 END), SUM(CASE WHEN T1.age > 19 AND T1.age <= 65 THEN 1 ELSE 0 END) AS adult , SUM(CASE WHEN T1.age > 65 THEN 1 ELSE 0 END) AS elder FROM client AS T1 INNER JOIN events AS T2 ON T1.client_id = T2.Client_ID WHERE T2.Product = 'Credit card'