Simple SQL Join help

[benphp]

I want to fetch the titles from the Courses table, but I only want the Course Title to return once when I join Events.

 

Courses

CID | CourseTitle 

 1  | Course A

 2  | Course B

 3  | Course C

 

Events

EID | CID | EventDate 

1   |  1  | 2016-02-22

2   |  1  | 2016-02-23

3   |  2  | 2016-02-24

4   |  3  | 2016-02-25

5   |  3  | 2016-02-26

 

If I use a JOIN, 

 

SELECT Courses.CourseTitle FROM Courses 

LEFT JOIN Events on (Events.CID = Courses.CID)

 

then I get

Course A

Course A

Course B

Course C

Course C

 

But what I want is

Course A

Course B

Course C

 

Because ultimately, I'm going to select an Event date range, and I want to see just the courses with the event date range.

 

Thanks!

Edited February 5, 2016 by benphp

[Barand]

SELECT DISTINCT Courses.CourseTitle ...

[benphp]

OK -thanks! Yes, that works. But what if I did this:

 

SELECT Courses.CourseTitle, Events.EventDate FROM Courses 

LEFT JOIN Events on (Events.CID = Courses.CID)

 

Distinct wouldn't work, right? 

[Barand]

Correct, it won't work in that case.

 

But that is the nature of joins. If you join one record with two matching records then the data from the one goes into both resulting records.

[kicken]

Just because your query will pull the course name for each row doesn't mean you have to display it in the output for each row however.

 

As you process the query results in your code you can detect when the course name has changed and only display it at that point. Alternatively you can have your code group the results by course then output the results with some nested loops.