Monthly Count In MySQL - mysql

Question

I'm going to do monthly COUNT.
I want to COUNT the data from now to 15 months ago.I want it to be marked 0 in the month when there is no data.
Here is My Table
PeopleFruit
Id
Fruit
People
CreatedAt
1
Apple
John
2020-11-13
2
Banana
Katie
2020-11-25
3
Kiwi
Sam
2021-03-03
4
Apple
Katie
2021-04-12
5
Apple
Katie
2021-04-24
6
Apple
John
2021-04-30
7
Banana
Sam
2021-09-02
8
Banana
Katie
2021-11-11
9
Apple
Sam
2021-12-12
10
Kiwi
John
2021-12-15
I want to know the fruit COUNT by month so that people don't overlap.
ex)If you look at Apple in April(Month 4), Katie chose it twice and John chose it once, but because Katie overlaps, COUNT became 2.
I used this query.
SELECT DATE_FORMAT(createdAt,'%y.%m') m, COUNT(DISTINCT(People)) as count
FROM PeopleFruit
WHERE createdAt > DATE_ADD(NOW(),INTERVAL - 15 MONTH)
AND Fruit = 'Apple'
GROUP BY m;
result is
m
count
20.11
1
21.04
2
21.12
1
But this is the result I want.
m
count
21.12
1
21.11
0
21.10
0
21.09
0
21.08
0
21.07
0
21.06
0
21.05
0
21.04
2
21.03
0
21.02
0
21.01
0
20.12
0
20.11
1
20.10
0
What should I do?

Answer 1

Since MySQL 8.0 you can use RECURSIVE CTE like:
WITH RECURSIVE months(m) AS (
SELECT DATE_FORMAT(NOW(),'%Y-%m-01') m
UNION ALL
SELECT DATE_SUB(m, INTERVAL 1 MONTH) m FROM months
WHERE m > DATE_SUB(NOW(), INTERVAL 15 MONTH)
) SELECT
DATE_FORMAT(months.m,'%y.%m') m,
COALESCE(count, 0) count
FROM months
NATURAL LEFT JOIN (
SELECT DATE_FORMAT(createdAt,'%Y-%m-01') m, COUNT(DISTINCT(People)) as count
FROM PeopleFruit
WHERE createdAt > DATE_ADD(NOW(),INTERVAL - 15 MONTH) AND Fruit = 'Apple'
GROUP BY m
) months_count ;
MySQL recursive CTE test