Get last 12 months of data grouped by month even if 0 - php

Question

I am trying to get a COUNT of the last 12 months of appointments grouped by month for output into a chart. The following works fine but I need it to return 0 if no results for each month.
$query = "SELECT COUNT(id) as total_month FROM appointments WHERE created >= DATE(NOW()) - INTERVAL 365 DAY GROUP BY Month(created)";
$query = $mysqli->real_escape_string($query);
if($result = $mysqli->query($query)){
while($row = $result->fetch_array())
{
$month_total_appointments .= $row['total_month'].',';
}
}
echo $month_total_appointments;
================================================================
Simple table structure and example for appointments Table
id customer_name created
1 John 2020-05-01 08:00:00 <= stored as datetime
2 Mike 2020-04-01 09:00:00
3 Steve 2020-02-01 10:00:00
Output would be 0,0,0,0,0,0,0,0,1,0,1,1
======================================================
Current output is: 1,1,1
I've read some use a month table and LEFT JOIN but everything i've tried doesn't seem to work. Can anyone help please?

Answer 1

You won't get zeroes for rows that aren't there. Grouping combines rows that match particular criteria, but it can't fabricate them out of nothing.
That's why it's typical to include the grouping criteria in the results:
SELECT COUNT(id), MONTH(created) AS created_month
FROM appointments
WHERE created >= DATE(NOW()) - INTERVAL 365 DAY
GROUP BY created_month
Then you can expand that in your application code to fill in the missing values. The alternative is you need a fully populated list of all possible dates to JOIN against.
Keep in mind the MONTH() thing will wrap around and group January 2020 with January 2021. You may want to split this up:
SELECT COUNT(id), YEAR(created) AS created_year, MONTH(created) AS created_month
FROM appointments
WHERE created >= DATE(NOW()) - INTERVAL 365 DAY
GROUP BY created_year, created_month