Including and excluding specific records - mysql

Question

I want to find some of buyer who had special condition (in this case, transaction >= 600000 called star member)
In this case, I want to find out star member (transaction >= 600000) who exists in January 2020 and March 2020, but it does not include star member who is doing transaction in February 2020.
here's my syntax
SELECT users_id
FROM order_star_member
GROUP BY users_id
HAVING SUM(CASE WHEN MONTHNAME(createdAt) = 'January'
THEN total_price_star_member END) >= 600000
AND SUM(CASE WHEN MONTHNAME(createdAt) = 'March'
THEN total_price_star_member END) >= 600000
AND NOT EXISTS (SELECT 1 FROM order_star_member
GROUP BY users_id
having sum(case when monthname(createdAt) = 'February'
THEN total_price_star_member END) >= 600000);
and here's my fiddle
https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=2c85037215fe71f700b51c8fd3a5ae76
on my fiddle, the expected result are the users_Id 15 because that id order at january and march but not in february

Answer 1

First in the inner t we group by month to determine all the star members.
The outer grouping groups by user_id. Their score is the sum of their star_member.
For February (m=2 (February being the second month) on the first line of the query below) if they are a star_member, they get an penalty (-100) as an arbitrary value that the SUM cannot overcome.
The only way a month_score=2 can exist if if a user has a star_member being true (1) for both January and March but not February.
SELECT users_id, SUM(IF(m=2 and star_member, -100, star_member)) as month_score
FROM
(SELECT users_id,
MONTH(createdAt) as m,
SUM(total_price_star_member) >= 600000 as star_member
FROM order_star_member
WHERE createdAt BETWEEN '20190101' AND '20190331'
GROUP BY users_id, m
) t
GROUP BY users_id
HAVING month_score=2
fiddle