SELECT check the colum of the max row - sql

Question

Here my row with my first select:
SELECT
user.id, analytic_youtube_demographic.age,
analytic_youtube_demographic.percent
FROM
`user`
INNER JOIN
analytic ON analytic.user_id = user.id
INNER JOIN
analytic_youtube_demographic ON analytic_youtube_demographic.analytic_id = analytic.id
Result:
---------------------------
| id | Age | Percent |
|--------------------------
| 1 |13-17| 19,6 |
| 1 |18-24| 38.4 |
| 1 |25-34| 22.5 |
| 1 |35-44| 11.5 |
| 1 |45-54| 5.3 |
| 1 |55-64| 1.6 |
| 1 |65+ | 1.2 |
| 2 |13-17| 10 |
| 2 |18-24| 10 |
| 2 |25-34| 25 |
| 2 |35-44| 5 |
| 2 |45-54| 25 |
| 2 |55-64| 5 |
| 1 |65+ | 20 |
---------------------------
The max value by user_id:
---------------------------
| id | Age | Percent |
|--------------------------
| 1 |18-24| 38.4 |
| 2 |45-54| 25 |
| 2 |25-34| 25 |
---------------------------
And I need to filter Age in ['25-34', '65+']
I must have at the end :
-----------
| id |
|----------
| 2 |
-----------
Thanks a lot for your help.
Have tried to use MAX(analytic_youtube_demographic.percent). But I don't know how to filter with the age too.
Thanks a lot for your help.

Answer 1

You can use the rank() function to identify the largest percentage values within each user's data set, and then a simple WHERE clause to get those entries that are both of the highest rank and belong to one of the specific demographics you're interested in. Since you can't use windowed functions like rank() in a WHERE clause, this is a two-step process with a subquery or a CTE. Something like this ought to do it:
-- Sample data from the question:
create table [user] (id bigint);
insert [user] values
(1), (2);
create table analytic (id bigint, [user_id] bigint);
insert analytic values
(1, 1), (2, 2);
create table analytic_youtube_demographic (analytic_id bigint, age varchar(32), [percent] decimal(5, 2));
insert analytic_youtube_demographic values
(1, '13-17', 19.6),
(1, '18-24', 38.4),
(1, '25-34', 22.5),
(1, '35-44', 11.5),
(1, '45-54', 5.3),
(1, '55-64', 1.6),
(1, '65+', 1.2),
(2, '13-17', 10),
(2, '18-24', 10),
(2, '25-34', 25),
(2, '35-44', 5),
(2, '45-54', 25),
(2, '55-64', 5),
(2, '65+', 20);
-- First, within the set of records for each user.id, use the rank() function to
-- identify the demographics with the highest percentage.
with RankedDataCTE as
(
select
[user].id,
youtube.age,
youtube.[percent],
[rank] = rank() over (partition by [user].id order by youtube.[percent] desc)
from
[user]
inner join analytic on analytic.[user_id] = [user].id
inner join analytic_youtube_demographic youtube on youtube.analytic_id = analytic.id
)
-- Now select only those records that are (a) of the highest rank within their
-- user.id and (b) either the '25-34' or the '65+' age group.
select
id,
age,
[percent]
from
RankedDataCTE
where
[rank] = 1 and
age in ('25-34', '65+');