Aggregate and count after left join - sql

Question

I am aggregating columns of a table to find the count of unique values. For example, aggregating
the status shows that out of 5 alerts there are 2 in open status and 3 that are closed. The simplified table looks like this:
create table alerts (
id,
status,
owner_id
);
The query below uses grouping sets to aggregate multiple columns at once. This approach works well.
with aggs as (
select status
from alerts
where alerts.owner_id = 'x'
)
select status, count(*)
from aggs
group by grouping sets(
(),
(status)
);
the output at its simplest could look like this:
status | count
--------+-------
| 1
new | 1
However, now I need to aggregate additional columns from another table. This table (shown below) can have zero or more rows associated to the first table (alerts:users 1:N).
create table users (
id,
alert_id,
name
);
I have tried updating the query to use a left join but this approach incorrectly inflates the counts of the alert columns.
with aggs as (
select alerts.status, users.name
from alerts
left join users on alerts.id = users.alert_id
where alerts.owner_id = 'x'
-- and additional filtering by columns in the users table
)
select status, name, count(*)
from aggs
group by grouping sets(
(),
(status),
(name)
);
Below is an example of the incorrect results. Since there are 3 rows in the user table the count
for the status column is now 3 but should be 1.
status | name | count
--------+-------------------------+-------
| | 3
| user1 | 1
| user2 | 1
| user3 | 1
new | | 3
How can I perform this aggregation to include the columns from the table with a many-to-one relationship without inflating the counts? In the future I will likely need to aggregate more columns from other tables with a many-to-one relationship and need a solution that will still work with several left joins. All help is much appreciated.
edit: link to db-fiddle https://www.db-fiddle.com/f/buGD2DuJiqf9LGF9rw5EgT/2

Answer 1

Do you just want to count the number of alerts? If so, use count(distinct):
count(distinct alert_id)
Of course, you need this in aggs, so the select would include:
alerts.id as alert_id