OCP-12c2019年CUUG OCP 071考试题库（76题）

Posted 2021-02-12

76、View the exhibit and examine the description of the DEPARTMENTSand EMPLOYEEStables.

The retrieve data for all the employees for their EMPLOYEE_ID, FIRST_NAME, and DEPARTMENT NAME, the following SQL statement was written:

SELECT employee_id, first_name, department_name

FROM employees

NATURAL JOIN departments;

The desired output is not obtained after executing the above SQL statement. What could be the reason for this?

A. The table prefix is missing for the column names in the SELECTclause.

B. The NATURAL JOINclause is missing the USINGclause.

C. The DEPARTMENTStable is not used before the EMPLOYEEStable in the FROMclause.

D. The EMPLOYEESand DEPARTMENTStables have more than one column with the same column name and data type.

Correct Answer: D

Section: (none) Explanation 解析：之前讲过，NATURAL JOIN 要求要有相同的列名和数据类型。using 只能用在 equiue join ，而且必须列的名字要相同，类型可以不同，但是可以 隐式转过去