LeetCode（180）：连续出现的数字 Consecutive Numbers（SQL）

2020.4.9 LeetCode 从零单刷个人笔记整理（持续更新）

github：https://github.com/ChopinXBP/LeetCode-Babel

传送门：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。

+----+-----+
| Id | Num |
+----+-----+
| 1  |  1  |
| 2  |  1  |
| 3  |  1  |
| 4  |  2  |
| 5  |  1  |
| 6  |  2  |
| 7  |  2  |
+----+-----+

例如，给定上面的 Logs 表， 1 是唯一连续出现至少三次的数字。

+-----------------+
| ConsecutiveNums |
+-----------------+
| 1               |
+-----------------+

---

SELECT DISTINCT l1.Num AS 'ConsecutiveNums'
FROM Logs l1, Logs l2, Logs l3
WHERE l1.Id = l2.Id - 1
    AND l1.Id = l3.Id -2
    AND l1.Num = l2.Num
    AND l1.Num = l3.Num;

SELECT DISTINCT Num AS ConsecutiveNums
FROM (
  SELECT Num,
    CASE
      WHEN @prev = Num THEN @count := @count + 1
      WHEN (@prev := Num) IS NOT NULL THEN @count := 1
    END AS CNT
  FROM Logs, (SELECT @prev := null,@count := null) AS t
) AS temp
WHERE temp.CNT >= 3

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