连续出现的数字。编写一个 SQL 查询，查找所有至少连续出现三次的数字。
答案是输出1，原因是1是唯一连续出现三次的数字。

DROP TABLE IF EXISTS logs;
CREATE TABLE logs (
  id int(11) NOT NULL,
  num int(11) NOT NULL,
  PRIMARY KEY (id)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

INSERT INTO logs VALUES ('1', '1');
INSERT INTO logs VALUES ('2', '1');
INSERT INTO logs VALUES ('3', '1');
INSERT INTO logs VALUES ('4', '2');
INSERT INTO logs VALUES ('5', '1');
INSERT INTO logs VALUES ('6', '2');
INSERT INTO logs VALUES ('7', '2');

sql语句如下：

SELECT DISTINCT
    l1.num AS ConsecutiveNums
FROM
    logs l1,
    logs l2,
    logs l3
WHERE
    l1.id = l2.id - 1
    AND l2.id = l3.id - 1
    AND l1.num = l2.num
    AND l2.num = l3.num

执行结果如下：