Melkij

ORDER BY ID

select * from pg_stats where tablename = 'table' and attname = 'column'

select ..., p.event_id is not null from events as e left join participations as p on p.user_id = ? and e.id = p.event_id

select ..., exists(select null from participations as p on p.user_id = ? and e.id = p.event_id) from events as e

select * from data where not exists (select from actives where data_id = data.id);

create type person_type as enum ('registrator', 'coordinator', 'user');
create table person (
id serial,
name person_type not null
);

select distinct on (raw_id) raw_id, id, single_sum 
from tablename
order by raw_id, id desc

Нужно получить диапазоны цен, где максимальная цена больше определенного числа.

select product_id, min(price), max(price) from prices group by product_id having max(price)>= ?

В таблице items 12 млн записей, в using_items 11 млн. Разумеется количество гипотетическое и маловероятное.

select admin_id
count(*) filter(where created_at >= '2019-01-01' and created_at < '2019-02-01'),
count(*) filter(where created_at >= '2019-02-01' and created_at < '2019-03-01'),
....
from tablename where ... group by admin_id