Select in Select MySQL - mysql

Question

I have two queries, i'd like if is possible execute in only one query as a Select in Select.
The first one:
SELECT
users.id
FROM users
LEFT JOIN users_date ON users_date.user = users.id
LEFT JOIN users_varchar ON users_varchar.user = users.id
WHERE
abilitato = 1
AND users_date.key = 'birthday'
AND users_varchar.key = 'nation'
AND users_varchar.value = 'US'
AND (users.reg_date >= '2013-05-31' AND users.reg_date <= '2013-05-31')
AND (floor(DATEDIFF(NOW(), users_date.value) / 365) >= 19 AND floor(DATEDIFF(NOW(), users_date.value) / 365) <= 19)
it retrieve a list of user id (filtered by Age, Nation or Date of registration)
the second one:
SELECT count(`matches`.`id`) FROM `matches` WHERE (`matches`.`status_home` = 3 AND `matches`.`status_guest` = 3) AND (`matches`.`team_home` = 13 OR `matches`.`team_guest` = 13)
i need perform the second select for every ID retrieved by the one's.
for every perform i must replace the value 13 with the id retrieved.
it is possible perform all in a single query with a select in select?
thanks advance for your help

Answer 1

Try this sql.
SELECT count(`matches`.`id`)
FROM `matches` m
INNER JOIN ( SELECT users.id as id
FROM users
LEFT JOIN users_date ON users_date.user = users.id
LEFT JOIN users_varchar ON users_varchar.user = users.id
WHERE abilitato = 1
AND users_date.key = 'birthday'
AND users_varchar.key = 'nation'
AND users_varchar.value = 'US'
AND (users.reg_date >= '2013-05-31' AND users.reg_date <= '2013-05-31')
AND (floor(DATEDIFF(NOW(), users_date.value) / 365) >= 19 AND floor(DATEDIFF(NOW(), users_date.value) / 365) <= 19)) t
on t.id=m.team_guest
WHERE (`matches`.`status_home` = 3 AND `matches`.`status_guest` = 3)
AND (`matches`.`team_home` = 13 OR `matches`.`team_guest` = t.id)
GROUP BY t.id

Answer 2

You can express what you want to do as an explicit join. But the question asks for a select within a select. For that, you need a correlated subquery. Here is the final query:
select users.id,
(SELECT count(`matches`.`id`)
FROM `matches`
WHERE (`matches`.`status_home` = 3 AND `matches`.`status_guest` = 3) AND
(`matches`.`team_home` = user.id OR `matches`.`team_guest` = users.id)
) as cnt
FROM users LEFT JOIN
users_date
ON users_date.user = users.id LEFT JOIN
users_varchar
ON users_varchar.user = users.id
WHERE abilitato = 1 AND users_date.key = 'birthday' AND
users_varchar.key = 'nation' AND users_varchar.value = 'US' AND
(users.reg_date >= '2013-05-31' AND users.reg_date <= '2013-05-31') AND
(floor(DATEDIFF(NOW(), users_date.value) / 365) >= 19 AND
floor(DATEDIFF(NOW(), users_date.value) / 365) <= 19
)
(The formatting helps me understand the query better.)
Doing this without a correlated subquery is a bit challenging because of the or in the matching condition.