PostgreSQL column does not exist when sub select - postgresql

Question

I have a table called user, and I need to get another users in an expecific distance range and the distance between them. My query is this:
select ( 6371 * acos(
cos( radians(users.latitude) )
* cos( radians(-22.9035) )
* cos( radians(-43.2096) - radians(users.longitude) )
+ sin( radians(users.latitude) )
* sin( radians(-22.9035) )
)
) as distance, users from users where users.id != 41 and distance > 50
I need to recover the user list and the distance, but the "as distance" is not working:
ERROR: column "distance" does not exist.
I tried with:
with distance as (
select ( 6371 * acos(
cos( radians(users.latitude) )
* cos( radians(-22.9035) )
* cos( radians(-43.2096) - radians(users.longitude) )
+ sin( radians(users.latitude) )
* sin( radians(-22.9035) )
)
) from users
)
select * from users where users.id != 41 and distance > 50
However, the error remains the same.

Answer 1

In Postgres, you cannot use column aliases in a where clause. That's why your first query does not work.
Your second query using a CTE can be made to work, but distance is a virtual table, not a column. Join with it.
with users_distance as (
select
id,
( 6371 * acos(
cos( radians(users.latitude) )
* cos( radians(-22.9035) )
* cos( radians(-43.2096) - radians(users.longitude) )
+ sin( radians(users.latitude) )
* sin( radians(-22.9035) )
)
) as distance
from users
)
select *
from users
join users_distance ud on users.id = ud.id
where users.id != 41 and ud.distance > 50
If you do this a lot, consider adding a generated column to the table so you don't have to recalculated it all the time.
alter table users add column distance numeric
generated always as (
6371 * acos(
cos( radians(users.latitude) )
* cos( radians(-22.9035) )
* cos( radians(-43.2096) - radians(users.longitude) )
+ sin( radians(users.latitude) )
* sin( radians(-22.9035) )
)
) stored
Try it
Finally, rather than doing these calculations yourself, consider using the very powerful PostGIS extension.