Create consecutive-numbers.sql

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MySQL/consecutive-numbers.sql

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+# Time:  O(n)
+# Space: O(n)
+#
+# Write a SQL query to find all numbers that appear at least three times consecutively.
+#
+# +----+-----+
+# | Id | Num |
+# +----+-----+
+# | 1  |  1  |
+# | 2  |  1  |
+# | 3  |  1  |
+# | 4  |  2  |
+# | 5  |  1  |
+# | 6  |  2  |
+# | 7  |  2  |
+# +----+-----+
+# For example, given the above Logs table, 1 is the only number that appears consecutively for at least three times.
+#
+
+# Write your MySQL query statement below
+SELECT  DISTINCT(Num) AS ConsecutiveNums
+FROM (
+    SELECT
+    Num,
+    @counter := IF(@prev = Num, @counter + 1, 1) AS how_many_cnt_in_a_row,
+    @prev := Num
+    FROM
+    Logs y
+    , (SELECT @counter:=1, @prev:=NULL) vars
+) sq
+WHERE how_many_cnt_in_a_row >= 3