sql query count number of record in a join - mysql

Question

I have to extract the list of POS(point of service) from pos table, based on location name:
POS
+----------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(100) | NO | | NULL | |
| address | varchar(200) | YES | | NULL | |
| country | varchar(45) | YES | | NULL | |
| location | varchar(100) | YES | | NULL | |
+----------+--------------+------+-----+---------+----------------+
so, it would be something like :
select *
from pos
where location = 'new york';
Now , from the table mission i have to count the number of POS (pos_name), and if this number is greater than a number coming from a subquery, pos register should not be shown.
mission
| id | int(11) | NO | PRI | NULL | auto_increment |
| team_name | varchar(45) | YES | | NULL | |
| team_photo | varchar(255) | YES | | NULL | |
| pos_name | varchar(45) | YES | | NULL | |
| pos_id | int(11) | YES | | NULL | |
| product_category | varchar(45) | YES | | NULL | |
| product_platform | varchar(45) | YES | | NULL | |
| created_by | int(11) | YES | | NULL | |
| judged_by | int(11) | YES | | NULL | |
| selfie_photo | varchar(255) | YES | | NULL | |
| like_score | int(11) | YES | | NULL | |
| star_score | float | YES | | NULL | |
| feedback_recommendation | varchar(2000) | YES | | NULL | |
| created_at | timestamp | YES | | CURRENT_TIMESTAMP | |
| updated_at | timestamp | YES | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
| sent_date | timestamp | YES | | NULL | |
| locked | tinyint(1) | YES | | 0 | |
+-------------------------+---------------+------+-----+-------------------+-----------------------------+
so until now i developed following sql query :
SELECT p.id,p.name
FROM missions m join pos p
on m.pos_id = p.id
where p.location = 'new york'
having count(m.pos_name) < (select count(*)
from product_category);
but this part of code
having count(m.pos_name)
should be something like that :
select count(*)
from missions
group by pos_name;
because without group by statement i will recieve a sum of all pos, but i need to check it for a group, not for all of them.
Any suggestion ?

Answer 1

I thing you need the data with group by with condition then try this
SELECT p.id,p.name
FROM missions m join pos p
on m.pos_id = p.id
where p.location = 'new york'
group by m.pos_name
having count(m.pos_name) < (select count(*)
from product_category);
Just add group by m.pos_name it will work.
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