【2019年8月】OCP 071認證考試最新版本的考試原題-第32題

choose three

Examine this SQL statement:

SELECT cust_id, cus_ last_name "Last Name"

FROM customers

WHERE country_id = 10

UNION

SELECT cust_id CUST_NO, cust_last_name

FROM customers

WHERE country_id = 30

Identify three ORDER BY clauses, any one of which can complete the query successfully.

A) ORDERBY 2, 1

B) ORDER BY "CUST_NO"

C) ORDER BY 2,cust_id

D) ORDER BY CUST_NO

E) ORDER BY "Last Name"

Answer：ACE

(解析：此題的解析跟下面的解析同樣，答案就是按照解析的總結規律找出來的。)

071-140 題目：

SELECT department_id "DEPT_ID", department_name, 'b' FROM departments

WHERE department_id=90 UNION

SELECT department_id, department_name DEPT_NAME, 'a' FROM departments

WHERE department_id=10

Which two ORDER BY clauses can be used to sort output?

A. ORDER BY DEPT_NAME;

B. ORDER BY DEPT_ID;

C. ORDER BY 'b';

D. ORDER BY 3;

Correct Answer: BD

(解析：經過實驗發現別名必須是用雙引號歸納起來的才能夠用來排序;並且發現取了別名(別名用雙引號歸納)的列的名字也不能用來排序;沒有用雙引號歸納起來的別名的列名能夠用來排序;order by 3，能夠根據顯示的列的順序進行排序。

注意 union 排序的的時候 order by 要寫在語句的最後;發現只能在第一條 select 語句中的列進行排序。)

SQL> select empno "CUST_NO",ename "LAST NAME",'a' FROM emp

2 UNION

3 SELECT EMPNO ,ENAME,'b' FROM emp

4 ORDER BY empno;

ORDER BY empno

*

第 4 行出現錯誤:

ORA-00904: "EMPNO": 標識符無效