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Databases

Joshua Duval
Joshua Duval
9,167 Points
Posted by Joshua Duval
Joshua Duval
9,167 Points

Query didn't perform the correct count

This is for Code Challenge: Counting Groups, Challenge Task 1 of 2.

I've tried multiple approaches to figuring this out. For some reason, when I run the query, it shows a blank row below genre with a genre count of 0. I'm not sure if this is the reason why it's not working, or if for some reason it's my query that is wrong. I've tried the challenge on more the one computer in multiple browsers, I still can't seem to get it to work.

SELECT genre, COUNT(genre) AS genre_count FROM books GROUP BY genre;

1 Answer

codebyamir
codebyamir
12,108 Points

You'll need to use COUNT(*) because that will also count NULL values whereas COUNT(genre) will not.

SELECT genre, COUNT(*) as genre_count from books GROUP BY genre;
Joshua Duval
Joshua Duval
9,167 Points
Joshua Duval
Joshua Duval
9,167 Points

Thank you! I guess I didn't fully understand the difference in the two methods. It makes more sense, now!

Thomas Helms
Thomas Helms
16,816 Points
Thomas Helms
Thomas Helms
16,816 Points

That's definitely helpful. So paraphrasing and clarifying, for my edification, COUNT(genre) doesn't count the number of NULL genre entries, while COUNT(*) will count each instance of NULL.