How to count all rows with multiple table joins and where conditions? - mysql

Question

I have the following tables:
create table loans
(
id int null,
status int null,
user_id int null
);
INSERT INTO loans VALUES (1, 1, 1);
INSERT INTO loans VALUES (2, 0, 1);
INSERT INTO loans VALUES (3, 1, 1);
create table deals
(
id int null,
status int null,
user_id int null
);
INSERT INTO deals VALUES (2, 0, 1);
INSERT INTO deals VALUES (3, 0, 1);
create table listings
(
id int null,
status int null,
user_id int null
);
INSERT INTO listings VALUES (1, 1, 1);
INSERT INTO listings VALUES (2, 1, 1);
INSERT INTO listings VALUES (3, 1, 1);
And have the following SQL:
SELECT COUNT(*) AS active_items
FROM loans
LEFT JOIN deals ON deals.user_id = 1
LEFT JOIN listings ON listings.user_id = 1
WHERE
loans.status = 1
AND deals.status = 1
AND listings.status = 1
AND loans.user_id = 1
The goal is to count all the rows where each table item has a status of 1, leaving out any that have a status of 0. My query which I have made seems to only return 0 all the time and I do not understand why? How can I query the database so I can find each loan, deal and listing which has a status of 1 and returns in one total called active_items? Why does my query not work?
DB Fiddle: https://www.db-fiddle.com/f/g9CoA9CdDujqzG4ZpgmJXh/1
The output for active_items is expected to be 5.

Answer 1

Don't use JOIN for this, since you're not relating the tables to each other. Just do 3 separate queries and add the counts.
SELECT SUM(count) AS total
FROM (
SELECT COUNT(*) AS count
FROM loans
WHERE user_id = 1 AND status = 1
UNION ALL
SELECT COUNT(*) AS count
FROM deals
WHERE user_id = 1 AND status = 1
UNION ALL
SELECT COUNT(*)
FROM listings
WHERE user_id = 1 AND status = 1
) AS x
DEMO

Answer 2

It is not 100% clear to me what you are trying to check.
But if I understand it correctly, I think the problem you have, is you are only checking for the user_id = 1, which might not have status 1 in all the tables (I really can't be sure without seeing your data).
I think you want to do something like:
SELECT COUNT(*) AS active_items
FROM loans
INNER JOIN deals ON deals.user_id = loans.user_id
INNER JOIN listings ON listings.user_id = loans.user_id
WHERE
loans.status = 1
AND deals.status = 1
AND listings.status = 1