CASE WHEN mySQL keeps getting error - mysql

Question

I am trying to use the CASE statement, but I keep getting a syntax error. I have followed the docs but I cannot seem to get rid of this syntax error:
query:
SELECT students.firstname, students.lastname, students.tnumber, grades.tnumber
FROM students, grades
CASE WHEN grades.tnumber=students.tnumber AND grades.courseid='CSC2110' AND (grades.Grade='A' OR grades.Grade='B' OR grades.Grade='C')THEN 'YES' ELSE 'NO' END
error:
error executing query. MySQL: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CASE WHEN grades.tnumber=students.tnumber AND grades.courseid='CSC2110' A' at line 1
Ignore the tables and select statements. I am more concerned are checking the syntax of my CASE statement and why it is throwing an error.

Answer 1

It isn't completely clear what you want the CASE expression to do, but it appears that it should be in the SELECT list. I also moved the join condition, which strangely appeared in the CASE expression, to the ON clause.
SELECT students.firstname,
students.lastname,
students.tnumber,
grades.tnumber,
CASE WHEN grades.courseid = 'CSC2110' AND
(grades.Grade='A' OR grades.Grade='B' OR grades.Grade='C')
THEN 'YES' ELSE 'NO' END AS someColumn
FROM students
INNER JOIN grades
ON grades.tnumber = students.tnumber

Answer 2

You can also try this one mate, using proper and readable syntax:
SELECT
s.tnumber, s.firstname, s.lastname,
IF (
-- condition
grades.Grade = 'A' OR grades.Grade = 'B' OR grades.Grade = 'C',
-- if true
'YES',
-- else
'NO'
) `status`
FROM
students s
INNER JOIN grades g ON g.tnumber = s.tnumber
WHERE grades.courseid = 'CSC2110';
Note
You can where that I have included a WHERE section where you can easily reuse this code with other courseid
I also added a suggested format when presenting data which is for people, always put the id code infront
One more point is that, by using a proper format, it help you and others to understand your code