Update SQL query for student report.sql based on grade rules

[Ingenuim]

Summary

This pull request updates the SQL query logic to match the specific business requirements set by Ketty:

• Displays student names only if their grade is 8 or higher.
• Replaces names with 'NULL' for students with grades less than 8.
• Orders students by:
  • Grade in descending order.
  • Name alphabetically for grade ≥ 8.
  • Marks in ascending order for grade < 8.

Changes Made

• Used INNER JOIN to match student marks with the correct grade range.
• Added a CASE statement in SELECT to conditionally display names.
• Implemented conditional logic in ORDER BY to sort differently based on grade level.

Why This is Needed

The logic ensures the report follows Ketty's formatting rules for visibility and sorting of student data, aligning with business expectations.