Question

I’ve made a query that works as needed when there is at least 1 row in the url_status table where u.urlid = us.urls however it won’t work if this isn’t true. What could I do to overcome this?

SELECT u.*, COUNT(*) AS historySize
FROM host_urls u, url_status us
WHERE u.publicationid = 1
AND us.urlid = u.urlid
GROUP BY u.urlid

Answer 1

You could use an outer join, specifically a left join, which will return at least one result row for each row in host_urls, even if it has no corresponding rows in url_status.

SELECT u.*, COUNT(*) AS historySize
FROM host_urls u
LEFT JOIN url_status us
ON us.urlid = u.urlid
WHERE u.publicationid = 1
GROUP BY u.urlid

You can replace the COUNT(*) with COUNT(us.urlid) (or another column from url_status) if it’s important that historySize be zero when there were no matching rows in url_status.