20. 다음 테이블 인스턴스(Instance)들에 대하여 오류 없이 동작하는 SQL(Structured Query Language) 문장은? STUDENT칼럼 이름데이터 타입키 타입설명studno숫자기본키학번name문자열이름grade숫자학년height숫자키deptno숫자학과 번호PROFESSOR칼럼 이름데이터 타입키 타입설명profno숫자기본키번호name문자열이름position문자열직급salary숫자급여deptno숫자학과 번호
- 1SELECT deptno, position, AVG(salary) FROM PROFESSOR GROUP BY deptno;

- 2(SELECT studno, name FROM STUDENT WHERE deptno = 101)UNION(SELECT profno, name FROM PROFESSOR WHERE deptno = 101);

- 3SELECT grade, COUNT(*), AVG(height) FROM STUDENT WHERE COUNT(*) > 2 GROUP BY grade;

- 4SELECT name, grade, height FROM STUDENT WHERE height > (SELECT height, grade FROM STUDENT WHERE name = ‘홍길동’);
