Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Development Tools Database Foundations SQL Calculating, Aggregating and Other Functions Grouping, Joining and Cleaning Up

Jonathan Weinstein
Jonathan Weinstein
9,063 Points
Posted by Jonathan Weinstein
Jonathan Weinstein
9,063 Points

Trouble creating OUTER JOIN

Having trouble completing the following challenge task:

Select the average "score" as "average", setting to 0 if null, by grouping the "movie_id" from the "reviews" table. Also, do an outer join on the "movies" table with its "id" column and display the movie "title" before the "average". Finally, filter out any "average" score over 2.

SELECT AVG(score), IFNULL(AVG(score),0) AS average FROM reviews LEFT OUTER JOIN reviews ON movies.id  GROUP BY movie_id HAVING average <= 2;

Anyone have guidance?

Thanks!

2 Answers

Leonardo Hernandez
Leonardo Hernandez
13,798 Points
Leonardo Hernandez
Leonardo Hernandez
13,798 Points

The first problem I see is you haven't selected the "'title' before the 'average' " After your 'SELECT' fit title in there and add a comma after it.

Next, select score as you did in the question before, with the average function, and setting AS average. Then wrap it all in the IFNULL function like below. (You selected score twice.)

IFNULL(AVG(score), 0) AS average)

Your join needs work too. This question has you select FROM movies as opposed to the previous two questions that had you select from reviews. It was a bit confusing. 

FROM movies LEFT OUTER JOIN reviews ON movies.id = reviews.movie_id

Finish it off with the GROUP BY and HAVING directions.

Antonio Nicasio
PLUS
Antonio Nicasio
Courses Plus Student 3,601 Points
Antonio Nicasio
Antonio Nicasio
Courses Plus Student 3,601 Points

SELECT movies.title, IFNULL(AVG(score),0) AS average FROM reviews RIGHT OUTER JOIN movies ON movies.id = reviews.movie_id GROUP BY movie_id HAVING average <= 2;