Personally I feel like SQL syntax is upside down, and things are used before they are defined.

SELECT 
a.id -- what the fuck is a?
, a.name
, b.city -- and b??
from users a -- oh 
join city b on a.id = b.user_id -- oh here's b

I’d expect it to instead be like

From users a
join city b on a.id = b.user_id
SELECT
a.id,
a.name,
b.city