SQL3_Completed

Problem 2: No. Of Passengers in Each Bus

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+# Write your MySQL query statement below
+WITH CTE AS( 
+SELECT p.passenger_id, p.arrival_time, MIN(b.arrival_time) AS bus_time
+FROM passengers p INNER JOIN buses b ON p.arrival_time <= b.arrival_time
+GROUP BY p.passenger_id)
+SELECT b.bus_id, COUNT(c.bus_time) AS 'passengers_cnt' FROM Buses b LEFT JOIN CTE c ON b.arrival_time = c.bus_time
+GROUP BY b.bus_id ORDER BY b.bus_id;

Problem 4: Dynamic Pivoting of a Table

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+CREATE PROCEDURE PivotProducts()
+BEGIN
+	# Write your MySQL query statement below.
+    SET SESSION GROUP_CONCAT_MAX_LEN = 10000000;
+    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 1');
+    PREPARE STATEMENT FROM @sql;
+    EXECUTE STATEMENT;
+    DEALLOCATE PREPARE STATEMENT;
+
+END

Problem-1 Consecutive Numbers

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+# Write your MySQL query statement below
+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;

Problem-3: User Activity

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+# Write your MySQL query statement below
+SELECT activity_date AS 'day', COUNT(DISTINCT user_id) AS active_users FROM Activity
+WHERE activity_date > '2019-06-27' AND activity_date <= '2019-07-27'
+#We can Use Between
+#WHERE activity_date BETWEEN '2019-06-28' AND '2019-07-27'
+GROUP BY activity_date; #GROUP BY 1;
+
+#Using DateDiff
+SELECT activity_date AS 'day', COUNT(DISTINCT user_id) AS active_users FROM Activity
+WHERE DATEDIFF('2019-07-27' , activity_date)>= 0 AND DATEDIFF('2019-07-27' , activity_date)<=29
+#WHERE DATEDIFF('2019-07-27' , activity_date) BETWEEN 0 AND 29
+GROUP BY 1;
+
+#Using DateSub
+SELECT activity_date AS 'day', COUNT(DISTINCT user_id) AS active_users FROM Activity
+WHERE activity_date BETWEEN DATE_SUB('2019-07-27', INTERVAL 29 DAY) AND '2019-07-27' GROUP BY 1;
+
+#Using DateAdd
+SELECT activity_date AS 'day', COUNT(DISTINCT user_id) AS active_users FROM Activity
+WHERE activity_date BETWEEN DATE_ADD('2019-07-27', INTERVAL -29 DAY) AND '2019-07-27' GROUP BY 1;
+
+#Using HAVING
+SELECT activity_date AS 'day', COUNT(DISTINCT user_id) AS active_users FROM Activity
+GROUP BY activity_date
+HAVING activity_date > '2019-06-27' AND activity_date <= '2019-07-27';