Question

I have two tables, Subject and Content, where Content references Subject with foreign key. I want to display how many times each subject appears in Content table (0, if it does not appear). But the query below only gives me the rows with count > 0 and ignores the others:

SELECT Subject.id, Subject.name, COUNT(Content.subject_id) AS `count`
FROM Subject LEFT JOIN Content
ON Subject.id = Content.subject_id
WHERE type = @type
GROUP BY Subject.id;

I checked and tried to follow this, this and this post but for some reason the code above does not work.

Any ideas?

Edit:
the type field is in the Content table and that was causing the the problem as “Will A” pointed out

Answer 1

Which table is type a column in? I’m supposing that it’s Content – and by including the field in the WHERE clause, you’re forcing the Content table on the right-hand side of the LEFT JOIN to have data in it (which means the LEFT JOIN is actually then just an INNER JOIN).

Try:

SELECT Subject.id, Subject.name, COUNT(Content.subject_id) AS `count`
FROM Subject
LEFT JOIN Content
ON Subject.id = Content.subject_id
AND type = @type
GROUP BY Subject.id;