8_the_report.sql

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

The STUDENTS table is described as follows
    +-----------+----------+
    | Column    |  Type    |
    +-----------+----------+
    | ID        | Integer  |
    | Name      | String   |
    | Marks     | Integer  |
    +-----------+----------+

Grades contains the following data:
    +-------+----------+----------+
    | Grade | Min_Mark | Max_Mark |
    +-------+----------+----------+
    | 1     | 0        | 9        |
    | 2     | 10       | 19       |
    | 3     | 20       | 29       |
    | 4     | 30       | 39       |
    | 5     | 40       | 49       |
    | 6     | 50       | 59       |
    | 7     | 60       | 69       |
    | 8     | 70       | 79       |
    | 9     | 80       | 89       |
    | 10    | 90       | 100      |
    +-------+----------+----------+

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.

- Sample input
    +-------+----------+----------+
    | ID    | Name     | Marks    |
    +-------+----------+----------+
    | 1     | Julia    | 88       |
    | 2     | Samantha | 68       |
    | 3     | Maria    | 99       |
    | 4     | Scarlet  | 78       |
    | 5     | Ashley   | 63       |
    | 6     | Jane     | 81       |
    +-------+----------+----------+

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

Note: Print "NULL"  as the name if the grade is less than 8.
*/

SELECT 
    CASE WHEN grade >= 8 THEN s.name
         ELSE NULL END as name, 
    g.grade, 
    s.marks
FROM
    students as s, 
    grades as g
WHERE 
    s.marks BETWEEN g.min_mark AND g.max_mark
ORDER BY
   g.grade DESC, 
   s.name;