How many cars running east have double-sided tail cars?
east is an direction; double-sided refers to sides = 'double'; tail refers to carsposition = trailPosi
SELECT COUNT(T1.id) FROM trains AS T1 INNER JOIN cars AS T2 ON T1.id = T2.train_id INNER JOIN ( SELECT train_id, MAX(position) AS trailPosi FROM cars GROUP BY train_id ) AS T3 ON T1.id = T3.train_id WHERE T1.direction = 'east' AND T2.position = T3.trailPosi AND T2.sides = 'double'
CREATE TABLE `cars` (
  `id` INTEGER NOT NULL,
  `train_id` INTEGER DEFAULT NULL,
  `position` INTEGER DEFAULT NULL,
  `shape` TEXT DEFAULT NULL,
  `len`TEXT DEFAULT NULL,
  `sides` TEXT DEFAULT NULL,
  `roof` TEXT DEFAULT NULL,
  `wheels` INTEGER DEFAULT NULL,
  `load_shape` TEXT DEFAULT NULL,
  `load_num` INTEGER DEFAULT NULL,
  PRIMARY KEY (`id`),
  FOREIGN KEY (`train_id`) REFERENCES `trains` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
);
CREATE TABLE `trains` (
  `id` INTEGER NOT NULL,
  `direction` TEXT DEFAULT NULL,
  PRIMARY KEY (`id`)
);
