Question

I am currently working on a school system where we have a parent course and a child course (meta_courses in Moodle).

So, we have a table mdl_course_meta and it has 3 fields. Id, parent_course and child_course.

My problem is that a parent course can have many child courses so that means, for example, a parent_course = 50 can appear two times in the table which means it has 2 child courses. I just want to be able to find all the parent courses without it returning the same value twice or more times. I’m currently using this query right now which obviously doesn’t do what I want:

$q = "SELECT * FROM mdl_course_meta";

I am working with PHP as well by the way.

Thanks a lot.

Answer 1

SELECT DISTINCT parent_course from mdl_course_meta

That should do it if you just want the course names. One thing to keep in mind, if you want other fields this is not going to work the way you want it to(how would it know which record to choose if there are multiple records with the same parent_course and you only want one).

This approach can only be used if you only want to return the parent_courses without duplicates.