Using conditional Update - On duplicate key update

Question

I have the following table called 'RESULT' that I get values for, from another table called 'Temp_main'

The fields in the 'RESULT' are like the following:

StudentName | SujectName | Result
---------------------------------
Adam        | Math       | Fail
Bob         | History    | Pass
Catherine   | Math       | Pass
Dave        | Science    | Fail
Evan        | History    | Pass

Primary key here is (StudentName,SubjectName)

I use the following code to get the data into the table:

insert into result(studentName,subjectName,result)
select StudentName,SubjectName,result
from temp_main

The temp_main table does not have the same primary key, so there are duplicate key values when I insert the data into result table.

Assume that a student appears for a test on the same subject more than once. All his attempts are on the temp_main table, while only his best result is on the Result table.

I am trying to get a ON DUPLICATE KEY UPDATE code that updates the result of a student-subject pair if and only if the latest result is 'Pass'

I tried

    insert into result(studentName,subjectName,result)
    select StudentName,SubjectName,result
    from temp_main
on duplicate key update result = case when temp_main(result) = 'Pass'
Then result(result)='Pass'

I am sure the this is crappy code. But I could not get any better solution.

Answer 1

You are missing an END from you SQL

INSERT INTO result(studentName,subjectName,result)
SELECT StudentName,SubjectName,result
FROM temp_main
ON DUPLICATE KEY UPDATE result.result = CASE WHEN result.result = 'Pass' THEN 'Pass' ELSE VALUES(result.result) END