Владимир Харсеев

SELECT count(*)
FROM users u
WHERE
  u.id IN ((
    SELECT o.user_id
    FROM orders o
    WHERE
      o.date < '2016-01-01' AND
      o.shop_id = 1 AND
      o.user_id NOT IN (SELECT user_id FROM orders WHERE shop_id <> 1 AND date < '2016-01-01')
  ) INTERSECT (
    SELECT o.user_id
    FROM orders o
    WHERE o.date >= '2016-01-01' AND o.shop_id <> 1
  ));