Completed Sql3

Sql3 Combined.sql

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+-- 1 Problem 1 : Consecutive Numbers	(https://leetcode.com/problems/consecutive-numbers/)
+
+select distinct l1.num as ConsecutiveNums
+from logs l1,logs l2, logs l3
+where l1.id = l2.id -1
+and l2.id = l3.id-1
+and l1.num = l2.num
+and l2.num = l3.num
+
+-- 2 Problem 2 :Number of Passengers in Each Bus 	(	https://leetcode.com/problems/the-number-of-passengers-in-each-bus-i/ )
+
+with CTE as(
+select p.passenger_id, p.arrival_time, min(b.arrival_time) as "btime"
+from Passengers p
+    inner join Buses b
+on p.arrival_time <= b.arrival_time
+group by p.passenger_id #,p.arrival_time
+)
+select b.bus_id, count(c.btime) "passengers_cnt"
+from Buses b
+left join CTE c
+on b.arrival_time = c.btime
+   group by b.bus_id
+    order by b.bus_id;
+
+-- 3 Problem 3 :User Activity		(https://leetcode.com/problems/user-activity-for-the-past-30-days-i/ )
+select distinct activity_date as day, count(distinct user_id) active_users
+from Activity
+where 
+-- activity_date between date_add('2019-07-27', interval -29 day) and '2019-07-27'
+-- activity_date between date_sub('2019-07-27', interval 29 day) and '2019-07-27'
+DATEDIFF('2019-07-27',activity_date) BETWEEN 0 AND 29
+--activity_date between '2019-06-28' and '2019-07-27'
+group by activity_date
+order by activity_date
+
+-- 4 Problem 4 :Dynamic Pivoting of a Table	(	https://leetcode.com/problems/dynamic-pivoting-of-a-table/ )
+
+CREATE PROCEDURE PivotProducts()
+BEGIN
+SET SESSION GROUP_CONCAT_MAX_LEN = 1000000; 
+select GROUP_CONCAT(DISTINCT CONCAT('sum(if(store = "',store,'", price, null)) as ',store)) INTO @sql from Products;
+SET @sql = CONCAT('select product_id, ',@sql, ' from Products group by product_id');
+select @sql;
+PREPARE STATEMENT from @sql;
+EXECUTE STATEMENT;
+DEALLOCATE PREPARE STATEMENT; 
+END