Can't Drop foreign key in MySQL

Question

I have had a 1 to many relationship between course and instructor, which I wanted to drop. When I tried to drop the instructorID in course table it told me that. I couldn't drop it as it was a foreign key. Then I decided to drop it like this:

ALTER TABLE course DROP FOREIGN KEY instructorID 

But i get this error :

#1091 - Can't DROP 'InstructorID'; check that column/key exists  

I don't get what this error means. what am i doing wrong?

Answer 1

Please run an SHOW CREATE TABLE course; to make sure instructorID is the name of foreign key constraint.

Additional: The error means MySQL searches for a foreign key constraint named "InstructorID" but there is no constraint with such name, maybe this is your column name, but you have to use the constraint name to delete foreign keys.

Answer 2

After you run SHOW CREATE table course; you should find the fk symbol which is commonly like the one bellow:

(course_ibfk_1)  

it may differ according to your mysql version you are using then drop the foreign key using the fk symbol as follow :

alter table course drop foreign key course_ibfk_1;