Question

Which of the following queries are legal?

(a) SELECT deptno, count(deptno) FROM emp GROUP BY ename;

(b) SELECT deptno, count(deptno), job FROM emp GROUP BY deptno;

(c) SELECT deptno, avg(sal) FROM emp;

(d) SELECT deptno, avg(sal) FROM emp GROUP BY deptno;

The question was posed to me in final exam.

I need to ask this question from Rapid Application Development topic in division Database Programming Techniques of Database Management

Answer 1

The correct choice is (d) SELECT deptno, avg(sal) FROM emp GROUP BY deptno;

To explain: For aggregate functions group by clause is necessary.