对于连接条件，将首先引用的表名放在 on 之后

SQL 代码规范 /

这样做的好处是，更容易判断你的连接是否会导致结果有 fanout 问题：

-- Good
select
    ...
from users
left join charges on users.id = charges.user_id
-- primary_key = foreign_key --> one-to-many --> fanout

select
    ...
from charges
left join users on charges.user_id = users.id
-- foreign_key = primary_key --> many-to-one --> no fanout

-- Bad
select
    ...
from users
left join charges on charges.user_id = users.id