Creating summary VIEW from fields from multiple tables - mysql

Question

I am trying to write a select query for creating a view in MySQL. Each row in the view should display weekly summary (sum, avg) for user values collected from multiple tables. The tables are similar to each-other but not identical. The view should include rows also in case other table doesn't have a values for that week. Something like this:
| week_year | sum1 | avg1 | sum2 | user_id |
| --------- | ---- | ---- | ---- | ------- |
| 201840 | | | 3 | 1 |
| 201844 | 45 | 55 | | 1 |
| 201845 | 55 | 65 | | 1 |
| 201849 | 65 | 75 | | 1 |
| 201849 | 75 | 85 | 3 | 2 |
The tables (simplified) are as follows:
CREATE TABLE IF NOT EXISTS `t1` (
`user_id` INT NOT NULL AUTO_INCREMENT,
`date` DATE NOT NULL,
`value1` int(3) NOT NULL,
`value2` int(3) NOT NULL,
PRIMARY KEY (`user_id`,`date`)
) DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS `t2` (
`id` INT NOT NULL AUTO_INCREMENT,
`date` DATE NOT NULL,
`value3` int(3) NOT NULL,
PRIMARY KEY (`id`)
) DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS `t3` (
`t3_id` INT NOT NULL,
`user_id` INT NOT NULL
) DEFAULT CHARSET=utf8;
My current solution doesn't seem reasonable and I am not sure how it would perform in case of thousands of rows:
select ifnull(yearweek(q1.date1), yearweek(q1.date2)) as week_year,
sum(value1) as sum1,
avg(value2) as avg1,
sum(value3) as sum2,
q1.user_id
from (select t2.date as date2,
t1.date as date1,
ifnull(t3.user_id, t1.user_id) as user_id,
t1.value1,
t1.value2,
t2.value3
from t2
join t3 on t3.t3_id=t2.id
left join t1 on yearweek(t1.date) = yearweek(t2.date) and t1.user_id = t3.user_id
union
select t2.date as date2,
t1.date as date1,
ifnull(t3.user_id, t1.user_id) as user_id,
t1.value1,
t1.value2,
t2.value3
from t2
join t3 on t3.t3_id=t2.id
right join t1 on yearweek(t1.date) = yearweek(t2.date) and t1.user_id = t3.user_id) as q1
group by week_year, user_id;
DB Fiddle
Is the current solution okay performance wise or are there better options? In case of in the future third (or fourth) table is added, how would I manage the query? Should I consider creating a separate table, that is updated with triggers?
Thanks in advance.

Answer 1

Another way you can do it is to union all the data and then group it. You'll have to perf test to see which is better:
SELECT
yearweek(date),
SUM(value1) as sum1,
AVG(value2) as avg1,
SUM(value3) as sum2
FROM
(
SELECT user_id, date, value1, value2, CAST(null as INT) as value3 FROM t1
UNION ALL
SELECT user_id, date, null, null, value3 FROM t2 INNER JOIN t3 ON t2.id = t3.t3_id
)
GROUP BY
user_id,
yearweek(date)
Hopefully mysql won't take issue with casting null to an int..