1) SELECT gender, count(name) FROM patients GROUP BY gender;2) SELECT count(name) FROM patients WHERE timestampdiff(YEAR,birth_date,curdate()) >= 40;3) SELECT name FROM patients WHERE timestampdiff(YEAR,last_visit_date,curdate())>= 1;4) SELECT count(name) FROM patients WHERE birth_date BETWEEN '1980-01-01' AND '1989-12-31'; 2)번과 3)의 쿼리는 아래와 같이 변경할 수 있다.2) SELECT COUNT(*) FROM patients WHERE birt..