[LeetCode] Consecutive Numbers (self join twice)

# Write your MySQL query statement below
SELECT DISTINCT
    l1.Num as ConsecutiveNums
FROM
    Logs l1
    JOIN Logs l2 ON l1.Id = l2.Id - 1
    JOIN Logs l3 ON l2.Id = l3.Id - 1
WHERE
    l1.Num = l2.Num AND l2.Num = l3.Num
;

 

self join 을 2번한다. 총 3개의 table이 join한다

 

결과

{"headers":

            ["Id", "Num", "Id", "Num", "Id", "Num"],

"values":

             [[1, 1, 2, 1, 3, 1],

             [2, 1, 3, 1, 4, 2],

             [3, 1, 4, 2, 5, 1],

             [4, 2, 5, 1, 6, 2],

             [5, 1, 6, 2, 7, 2]]}

 

따라서 l1.num = l2.num = l2.num 인 row 중에서(WHERE)

l1.num을 distinct한 결과만 column rename(as) 해서 출력