Query question-1z0-001 exam

Question

a question from 1z0-001
Examine the structure of the STUDENTS table:
STUDENT_ID NUMBER NOT NULL, Primary Key STUDENT_NAME VARCHAR2(30) COURSE_ID VARCHAR2(10) NOT NULL MARKS NUMBER START_DATE DATE FINISH_DATE DATE
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;
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 ;
Answer: D
i try the two queries i don't see any difference between them..then why is the answer d ..
thank u
rajiv

Answer 1

i try the two queries i don't see any difference between them..then why is the answer d Of course answer is D. But, A and D gives definately different results.
Query A takes the first 10 records from the table, gives the results.
Query D takes the results from the marks desc order and choose 10 records from the row source.
Jaffar