Mysql - Run a user query for all users - mysql

Question

I have a user specific query which i need to run for all users.
I am struggling on how to replace the hard coded uuid with a reference or if it needs a different approach altogether?
select max(MaxDate), users.created_at
from (
select max(`moment`.`created_at`) as MaxDate
from `moment`
where `moment`.`user_uuid` = "7dd668af-241a-4176-a1da-f5689214b206"
union (
select max(`module`.`updated_at`) as MaxDate
from `module`
where `module`.`user_uuid` = "7dd668af-241a-4176-a1da-f5689214b206"
)
) as stuff, `users`
where `users`.`uuid` = "7dd668af-241a-4176-a1da-f5689214b206"
the end goal is to get the date a user was created and a date the same user last updated something and then get the avage time between them. But for all users not a single user.

Answer 1

Here is a general query which would report all users, sorted by user:
SELECT
u.user_uuid,
GREATEST(COALESCE(t1.max_created_at, t2.max_updated_at),
COALESCE(t2.max_updated_at, t1.max_created_at)) AS max_date
FROM users u
LEFT JOIN
(
SELECT user_uuid, MAX(created_at) AS max_created_at
FROM moment
GROUP BY user_uuid
) t1
ON u.user_uuid = t1.user_uuid
LEFT JOIN
(
SELECT user_uuid, MAX(updated_at) AS max_updated_at
FROM module
GROUP BY user_uuid
) t2
ON u.user_uuid = t2.user_uuid
ORDER BY
u.user_uuid;
If you want to restrict to a single user, you may still do so via a WHERE clause or via a WHERE IN clause for a group of users.
Note that there is a bit of a smell in your database design, because you have your user information strewn across multiple tables. My answer assumes that in general every user would appear in both tables, but maybe this is not the case.

Answer 2

Use group by
select `users`.`uuid`,max(MaxDate) as maxdate, min(users.created_at) as createddate
from (
select `moment`.`user_uuid`,max(`moment`.`created_at`) as MaxDate
from `moment`
group by `moment`.`user_uuid`
union
select `module`.`user_uuid`,max(`module`.`updated_at`) as MaxDate
from `module` group by `module`.`user_uuid`
) as stuff inner join `users` on `users`.`uuid`=stuff.user_uuid
group by `users`.`uuid`