【第31题】OCP认证1Z0-071最新考试题库及答案

071考试不仅是OCP11g的考试科目，同时也是OCP 12c的考试科目，所以关心071考题的同学有很多，对此我们专门收集整理了近期071考试的原题，并对这些考题进行讲解，希望帮助广大考生顺利通过071考试。

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071考题解析-第31题、choose the best answer:

Examine the structure of the EMPLOYEES table:

There is a parent/child relationship between EMPLOYEE_ID and MANAGER_ID.

You want to display the name, joining date, and manager for all the employees.

Newly hired employees are yet to be assigned a department or a manager. For them, 'No Manager' should be displayed in the MANAGER column.

Which SQL query gets the required output?

A) SELECT e.last_name, e.hire_date, NVL(m.last_name, 'No Manager') Manager

FROM employees e RIGHT OUTER JOIN employees m

ON (e. manager_id = m.employee_id);

B) SELECT e.last_name, e.hire_date, NVL(m.last_name, 'No Manager') Manager

FROM employees e JOIN employees m

ON (e.manager_id = m.employee_id);

C) SELECT e.last_name, e.hire_date, NVL(m.last_name, 'No Manager') Manager

FROM employees e LEFT OUTER JOIN employees m

ON (e.manager_id = m.employee_id);

D) SELECT e.last_name, e.hire_date, NVL(m.last_name, 'No Manager') Manager

FROM employees e NATURAL JOIN employees m

ON (e.manager_id = m.employee_id);

Answer：C

(解析：因为员工 king 是没有经理的，但是也要显示出来，因为是在经理号这边缺少数据，所以这里要用左外连接。注意左右的区别：

SELECT e.last_name, e.hire_date, NVL(m.last_name, 'No Manager') Manager

FROM employees e , employees m

WHERE e.manager_id = m.employee_id(+);

)

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