A SQL on case

Example: from the Stud_grade table for all students examination results, where the results are NULL output "not tested", less than 60 points output "fail", 60 to 70 points output "pass", 70 points to 90 points output "good", greater than or equal to 90 ticks output "excellent".

SELECT
     Stud_id,
     NAME,
     Score = CASE
WHEN grade IS NULL THEN
     ‘untested’
WHEN grade < 60 THEN
     'failed'
WHEN grade >= 60
AND grade < 70 THEN
     'passage'
WHEN grade >= 70
AND grade < 90 THEN
     'good'
WHEN grade >= 90 THEN
     'excellent'
END
FROM
     Stud_grade

A SQL on case