https://www.hackerrank.com/challenges/the-report/problem

📔문제

You are given two tables: Students and Grades. Students contains three columns ID, Name and Marks.

Grades contains the following data:

Ketty gives Eve a task to generate a report containing three columns: Name, Grade and Mark. Ketty doesn't want the NAMES of those students who received a grade lower than 8. The report must be in descending order by grade -- i.e. higher grades are entered first. If there is more than one student with the same grade (8-10) assigned to them, order those particular students by their name alphabetically. Finally, if the grade is lower than 8, use "NULL" as their name and list them by their grades in descending order. If there is more than one student with the same grade (1-7) assigned to them, order those particular students by their marks in ascending order.

Write a query to help Eve.

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📝예시

Maria 10 99
Jane 9 81
Julia 9 88 
Scarlet 8 78
NULL 7 63
NULL 7 68

Print "NULL" as the name if the grade is less than 8.

Consider the following table with the grades assigned to the students:

So, the following students got 8, 9 or 10 grades:

Maria (grade 10) Jane (grade 9) Julia (grade 9) Scarlet (grade 8)

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🧮분야

• JOIN

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📃SQL 코드

select name, grade, students.marks
from students,grades
where students.marks between min_mark and max_mark
and grade>=8
order by grade desc, name;

select 'NULL', grade, students.marks mark
from students,grades
where students.marks between min_mark and max_mark
and grade<8
order by grade desc, mark;

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📰출력 결과

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📂고찰

두 테이블을 따로 만들어서 결과를 출력했다.

만약 grade가 8 이상이라면, grade desc, name순으로 정렬을 해야하고,
만약 grade가 8미만이라면, 이름 자리엔 'NULL'을 출력하며 grade, mark순으로 정렬해야 한다.