Homework SQL3

activity.sql

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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'
+-- GROUP BY activity_date ;
+
+# Using BETWEEN date1 AND date2 (both inclusive)
+-- SELECT activity_date AS 'day', COUNT(DISTINCT user_id) AS 'active_users'
+-- FROM Activity
+-- WHERE activity_date BETWEEN '2019-06-28' AND '2019-07-27'
+-- GROUP BY 1;
+
+# Using DATEDIFF(date1, date2)
+-- SELECT activity_date AS 'day', COUNT(DISTINCT user_id) AS 'active_users'
+-- FROM Activity
+-- WHERE  DATEDIFF('2019-07-27', activity_date) BETWEEN 0 AND 29
+-- GROUP BY 1;
+
+# Using DATE_SUB(date, INTERVAL expr unit) 
+-- 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 activity_date;
+
+# Using DATE_ADD(date, INTERVAL expr unit) 
+-- 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 activity_date;
+
+# Using Having clause ---> GROUP BY clause always comes before Having Clause 
+-- 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'
+
+SELECT activity_date AS 'day', COUNT(DISTINCT user_id) AS 'active_users'
+FROM Activity
+GROUP BY activity_date
+HAVING activity_date BETWEEN '2019-06-27' AND '2019-07-27';

consecutiveNums.sql

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+# Write your MySQL query statement below
+SELECT DISTINCT l1.num AS 'ConsecutiveNums' FROM Logs l1, Logs l2, Logs l3
+WHERE l2.id -1 = l1.id
+AND l3.id -1 = l2.id
+AND l1.num = l2.num
+AND l2.num = l3.num;

dynamicPivotingTable.sql

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+CREATE PROCEDURE PivotProducts()
+BEGIN
+	# Write your MySQL query statement below.
+    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 1');
+    PREPARE stmt FROM @sql;
+    EXECUTE stmt;
+    DEALLOCATE PREPARE stmt;
+END

passengersInBus.sql

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+CREATE TABLE Buses (
+    bus_id INT,
+    arrival_time INT
+);
+
+CREATE TABLE Passengers (
+    passenger_id INT,
+    arrival_time INT
+);
+
+INSERT INTO Buses (bus_id, arrival_time) VALUES
+(1, 2),
+(2, 4),
+(3, 7);
+
+INSERT INTO Passengers (passenger_id, arrival_time) VALUES
+(11, 1),
+(12, 5),
+(13, 6),
+(14, 7);
+
+
+WITH CTE AS(SELECT p.passenger_id, p.arrival_time, MIN(b.arrival_time) AS bus_arrival_time
+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(CTE.bus_arrival_time) AS 'passenger_count'
+FROM Buses b
+LEFT JOIN CTE
+ON b.arrival_time = CTE.bus_arrival_time
+GROUP BY b.bus_id;