Akina

При этом по факту я спокойно вставляю в таблицу произвольную строку и никакой проверки не происходит, данные спокойно записываются в таблицу.

ОШИБКА: в целевой внешней таблице "users" нет ограничения уникальности, соответствующего данным ключам

FOREIGN KEY(user_id) REFERENCES users (user_id)

SELECT *
FROM table t1 
JOIN table t2
WHERE t1.id > t2.id
  AND ST_Intersect(t1.geom, t2.geom)

WITH
cte1 AS (
  SELECT jsonb_build_object('name',   users.name, 
                           'value',  comments.value,
                           'rating', comments.rating) single_user,
         comments.order_id,
         'comment' || ROW_NUMBER() OVER (PARTITION BY comments.order_id ORDER BY comments.id) num
  FROM users
  JOIN comments ON users.id = comments.user_id
),
cte2 AS (
  SELECT jsonb_build_object('order_id', order_id) ||
         jsonb_object_agg(num, single_user) single_order
  FROM cte1
  GROUP BY order_id
)
SELECT jsonb_agg(single_order) final_data
FROM cte2;

with cte (cnt) as (
  select count(*)
  from test_sender 
  where statuse='crash'
  )
delete 
  from test_sender 
  using cte
  where cte.cnt = 0;

CREATE FUNCTION fn_test() 
RETURNS TRIGGER
AS $fn_test$
BEGIN
    IF OLD.val1 <> NEW.val1 THEN   -- задать условие
        NEW.id := NEW.id * 10;     -- выполнить действие
    END IF;
    RETURN NEW;
END;
$fn_test$ LANGUAGE plpgsql;

CREATE TRIGGER tr_test
BEFORE UPDATE ON test
FOR EACH ROW
EXECUTE FUNCTION fn_test();

CREATE FUNCTION fn_test() 
RETURNS TRIGGER
AS $fn_test$
BEGIN
    NEW.id := NEW.id * 10;     -- выполнить действие
    RETURN NEW;
END;
$fn_test$ LANGUAGE plpgsql;

CREATE TRIGGER tr_test
BEFORE UPDATE ON test
FOR EACH ROW
WHEN (OLD.val1 <> NEW.val1)   -- задать условие
EXECUTE FUNCTION fn_test();

select * 
from products 
order by type ASC,
         case WHEN type = 'books' then id      ELSE 0 END desc,
         case WHEN type = "food"  then name    ELSE 0 END asc,
         case WHEN type = "food"  then price   ELSE 0 END desc,
         case WHEN type = "relax" THEN popular ELSE 0 END asc,
         case WHEN type = "relax" THEN id      ELSE 0 END desc

CREATE TABLE tasks (
    id PRIMARY KEY,
    definition,
    performer_id REFERENCES performer (id)
    expired_at DATETIME
);

UPDATE tasks
SET performer_id = @performer_idб
    expired_at  = NOW() + INTERVAL 'performing time'
WHERE ( expired_at IS NULL or expired_at < NOW() )
  AND ( id = @task_id )

SELECT '2022-04-01 09:23:45'::DATE, '2022-04-01 09:23:45'::TIME