OCP-1Z0-051 补充题库 第16题 rownum的用法

一、原题

Examine the structure of the STUDENTS table:



You need to create a report of the 10 students who achieved the highest ranking in the course INT

SQL and who completed the course in the year 1999.

Which SQL statement accomplishes this task?

A.
SELECT student_ id, marks, ROWNUM "Rank"

  FROM students

 WHERE ROWNUM <= 10

   AND finish_date BETWEEN '01-JAN-99' AND '31-DEC-99

AND course_id = ' INT_SQL '

ORDER BY marks DESC;
B.
SELECT student_id, marks, ROWID "Rank"

  FROM students

 WHERE ROWID <= 10

   AND finish_date BETWEEN '01-JAN-99' AND '31-DEC-99'

   AND course_id = 'INT_SQL'

 ORDER BY marks;
C.
SELECT student_id, marks, ROWNUM "Rank"

  FROM (SELECT student_id, marks

          FROM students

         WHERE ROWNUM <= 10

           AND finish_date BETWEEN '01-JAN-99' AND '31-DEC-99'

           AND course_id = 'INT_SQL'

         ORDER BY marks DESC);
D.
SELECT student_id, marks, ROWNUM "Rank"

  FROM (SELECT student_id, marks

          FROM students

         WHERE finish_date BETWEEN ’01 - JAN - 99 AND ’31 - DEC - 99’

           AND course_id = ‘INT_SQL’

         ORDER BY marks DESC)

 WHERE ROWNUM <= 10;

E.
SELECT student id, marks, ROWNUM “Rank”

  FROM (SELECT student_id, marks FROM students ORDER BY marks)

 WHERE ROWNUM <= 10

   AND finish date BETWEEN ’01 - JAN - 99’ AND ’31 - DEC - 99’

   AND course_id = ‘INT_SQL’;

答案: D

二、题目翻译

看下面的STUDENTS表的结构：

现在要建一个报表，科目是INT_SQL最高的、并且是在1999年完成的10个学生。

下面哪个sql语句能完成这个任务?

三、题目解析

rownum是显示序号，要显示最高的前10名，需要先按降序排列，再取rownum<=10;