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

Posted by Jami Schwarzwalder
Jami Schwarzwalder
17,961 Points

There is something wrong with your query. Challenge Task 3 of 3

I'm on the third Task in the Grouping, Joining, and Cleaning Up Challenge.

I believe I've written everything accurately, but my JOIN may not be working correctly.

Jason Anello
Jason Anello
Courses Plus Student 94,592 Points

Hi Jami,

Can you post what you've tried if you're still stuck on this?

2 Answers

Jason Anello
Jason Anello
Courses Plus Student 94,592 Points

You're pretty close with that.

In this part:

ON reivews.movie_id = movies.reviews_id

You have a typo on reviews and the id in the movies table is id not reviews_id

The only other issue is the order that you have your tables around the LEFT OUTER JOIN

reviews LEFT OUTER JOIN movies

With a left join, the table you place on the left side will have all of its rows included but the table on the right will not necessarily have all of its rows included. With it set like this we will get all of the movies that have a review but we will be missing any movies from the movies table that never got a review.

In this case, we need to make sure we've included all the movies from the movies table whether they have a review or not.

Jami Schwarzwalder
Jami Schwarzwalder
17,961 Points
Jami Schwarzwalder
Jami Schwarzwalder
17,961 Points

I'm sorry I thought it attached my code

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