MySQL 复杂的 in 子查询语句会导致筛选失效？

导入数据

CREATE TABLE test (
	id INT UNSIGNED auto_increment PRIMARY KEY,
	shop_id INT (11) UNSIGNED NOT NULL
);
INSERT INTO test (id, shop_id) VALUES (1, 1);
INSERT INTO test (id, shop_id) VALUES (2, 2);
INSERT INTO test (id, shop_id) VALUES (3, 3);
INSERT INTO test (id, shop_id) VALUES (4, 2);

使用语句查询，目的是找出每个 shop_id 下第一个 id

SELECT * FROM test WHERE id IN ( SELECT `t`.`id` FROM ( SELECT e.* FROM test e ORDER BY e.id DESC ) t GROUP BY `t`.`shop_id` );

结果第四条记录也被查询了出来，而子查询语句如果单独拉出来执行，结果是 1,2,3 。这是为什么？