【2019年8月版本】OCP 071認證考試最新版本的考試原題-第1題

Choose the best answer.

Exanine the desciption of the EMPLOYEES table:

Nane Null Type

---

EMP_ID NOT NUL NUMBER

EMP_NAME VARCHAR2 (40)

DEPT_ID NUMBER(2)

SALARY NUMBER(8,2)

JOIN_DATE DATE

Which query is valid?

A) SELECT dept_id, join_date, SUM(salary) FROM employees GROUP BY dept_id,join_date;

B) SELECT depe_id,join_date, SUM(salary) FROM employees GROUP BY dept_id:

C) SELECT dept_id,MAX (AVG (salary)) FROM employees GROUP BY dept_id;

D) SELECT dept_ id,AVG (MAX (salary)) FROM employees GROUP BY dapt_id;

Anser:A

(解析：sum 函數若是遇到空值會跳過，不會形成最後的值爲空。

其它的查詢會出現錯誤：

SQL> select avg(max(sal)) from emp2 group by deptno;

AVG(MAX(SAL))

---

3616.66667

SQL> select deptno,avg(max(sal)) from emp2 group by deptno;

select deptno,avg(max(sal)) from emp2 group by deptno

*

第 1 行出現錯誤:

ORA-00937: 不是單組分組函數

)