Medium LC Problem = ConsecutiveNumbers.sql

LeetCode/SQL50/ConsecutiveNumbers.sql

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+-- Table: Logs
+
+-- +-------------+---------+
+-- | Column Name | Type    |
+-- +-------------+---------+
+-- | id          | int     |
+-- | num         | varchar |
+-- +-------------+---------+
+-- In SQL, id is the primary key for this table.
+-- id is an autoincrement column.
+
+-- Find all numbers that appear at least three times consecutively.
+
+-- Return the result table in any order.
+
+-- The result format is in the following example.
+
+-- Example 1:
+
+-- Input: 
+-- Logs table:
+-- +----+-----+
+-- | id | num |
+-- +----+-----+
+-- | 1  | 1   |
+-- | 2  | 1   |
+-- | 3  | 1   |
+-- | 4  | 2   |
+-- | 5  | 1   |
+-- | 6  | 2   |
+-- | 7  | 2   |
+-- +----+-----+
+-- Output: 
+-- +-----------------+
+-- | ConsecutiveNums |
+-- +-----------------+
+-- | 1               |
+-- +-----------------+
+-- Explanation: 1 is the only number that appears consecutively for at least three times.
+
+-- Write your PostgreSQL query statement below
+-- Solution
+with computed_tb as (
+    select X.id Xid,
+            X.num Xnum,
+            Y.id Yid,
+            Y.num Ynum,
+            Y.id - X.id as diff
+        from Logs X cross join Logs Y 
+        where Y.id - X.id in (1) and X.num = Y.num
+)
+select distinct A.Xnum as ConsecutiveNums
+from computed_tb A join computed_tb B on (A.Xid = B.Yid) 
+where A.Xnum in (
+    select Xnum from computed_tb group by Xnum having count(Xnum) >= 2
+)