feat: problem 1 added

problem1-180-consecutive-numbers.sql

@@ -0,0 +1,35 @@
+select
+    distinct log1.num as ConsecutiveNums
+from
+    Logs log1,Logs log2,Logs log3
+where log1.id = log2.id - 1
+and log2.id = log3.id -1
+and log1.num =log2.num
+and log2.num =log3.num
+
+
+-- join
+SELECT DISTINCT log1.num as ConsecutiveNums
+FROM Logs log1
+JOIN Logs log2 ON log1.id = log2.id - 1
+JOIN Logs log3 ON log2.id = log3.id - 1
+WHERE log1.num = log2.num
+  AND log2.num = log3.num
+
+
+--window function
+WITH ThreeConsecutive AS (
+  SELECT
+    CASE
+      WHEN num = LAG(num, 1) OVER (ORDER BY id)
+        AND num = LAG(num, 2) OVER (ORDER BY id)
+      THEN num
+    END AS ConsecutiveNums
+  FROM Logs
+)
+
+SELECT
+    DISTINCT ConsecutiveNums
+FROM ThreeConsecutive
+WHERE
+    ConsecutiveNums IS NOT NULL;

problem2-2142-number-of-passanger-bus.sql

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+WITH bus_time_passenger AS (
+    SELECT
+        p.passenger_id,
+        MIN(b.arrival_time) AS bus_time
+    FROM
+        Passengers p
+    LEFT JOIN
+        Buses b
+        ON p.arrival_time <= b.arrival_time
+    GROUP BY
+        p.passenger_id
+)
+
+SELECT
+    b.bus_id,
+    COUNT(bp.bus_time) AS passengers_cnt
+FROM
+    Buses b
+LEFT JOIN
+    bus_time_passenger bp
+    ON bp.bus_time = b.arrival_time
+GROUP BY
+    b.bus_id
+ORDER BY
+    b.bus_id;

problem3-1141-user-activity-30days.sql

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+select
+activity_date as day,
+count(distinct user_id) as active_users
+from Activity
+where activity_date >  DATE_SUB('2019-07-27', INTERVAL 30 DAY)
+and activity_date <= '2019-07-27'
+group by activity_date
+order by activity_date

problem4-2252-dynemic-pivot-table.sql

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+CREATE PROCEDURE PivotProducts()
+BEGIN
+
+    SET SESSION GROUP_CONCAT_MAX_LEN = 10000000;
+    SET @cols = (
+    SELECT 
+        GROUP_CONCAT( DISTINCT   
+        CONCAT('MAX(IF(store = ''',store,''', price, NULL)) AS ', store) 
+        )
+    FROM Products order by store);
+
+    SET @query = CONCAT('SELECT product_id, ', @cols, ' FROM Products GROUP BY product_id ;');
+
+
+    PREPARE stmt FROM @query;
+    EXECUTE stmt;
+
+
+END