mysql problem when doing 2 counts in the same query - mysql

Question

First of all, apologies if this seems like a very dumb question, I have just started working with mySQL.
I have 2 tables:
1- Customer_courier_chat
2- Orders
Basically I want to do a query to count the amount of messages from a customer and the amount of messages from a courier. When I do an individual query to look for it, it works well but when I do both in the same query it returns different values.
The following query provides good results:
SELECT o.*, count(j.from_id) AS messages_courier
FROM test.orders o
INNER JOIN test.customer_courier_chat_messages j ON j.from_id = j.courier_id and o.order_id = j.order_id
Group BY o.order_id;
Results of the previous query messgaes from courier
The following one also provides good results:
SELECT o.*, count(k.from_id) AS messages_customer
FROM test.orders o
INNER JOIN test.customer_courier_chat_messages k ON k.from_id = k.customer_id and o.order_id = k.order_id
Group BY o.order_id;
Results of the previous query messages from customer
The main problem comes when I try to do both in the same query as the output is not correct.
SELECT o.*, count(j.courier_id) messages_courier, count(k.from_id) AS messages_customer
FROM test.orders o
INNER JOIN test.customer_courier_chat_messages j ON j.from_id = j.courier_id and o.order_id = j.order_id
INNER JOIN test.customer_courier_chat_messages k ON k.from_id = k.courier_id and o.order_id = k.order_id
Group BY o.order_id;
Results of previous query not working
Based on the results of the 2 invidiual queries, the previous one should provide:
order_id |city_code |messages_courier |messages_customer|
59528555 | ES | 2 | 5 |
11223344 | FR | 3 | 4 |
But, it actually provides:
order_id |city_code |messages_courier |messages_customer|
59528555 | ES | 4 | 4 |
11223344 | FR | 9 | 9 |
Am I missing something?
Thank you in advanced.
Kindly regards,
J

Answer 1

You can do it with conditional aggregation:
SELECT o.order_id, o.city_code,
SUM(m.from_id = m.courier_id) AS messages_courier,
SUM(m.from_id = m.customer_id) AS messages_customer
FROM test.orders o INNER JOIN test.customer_courier_chat_messages m
ON o.order_id = m.order_id
GROUP BY o.order_id, o.city_code;

Answer 2

You are first joining the table then using the count. You have to first pick get the count then use the join -
SELECT o.*, j.cnt messages_courier, k.cnt AS messages_customer
FROM test.orders o
INNER JOIN (SELECT order_id, COUNT(*) CNT
FROM test.customer_courier_chat_messages
WHERE from_id = courier_id
GROUP BY order_id) j ON o.order_id = j.order_id
INNER JOIN (SELECT order_id, COUNT(*) CNT
FROM test.customer_courier_chat_messages
WHERE from_id = customer_id
GROUP BY order_id) k ON o.order_id = k.order_id;