SQL BI-WEEKLY ASSESSMENT Solution Blessing Adeyemi.txt

# Write your MySQL query statement below: 
SELECT E1.name AS Employee
FROM Employee AS E1
INNER JOIN Employee AS E2 ON E1.Managerid = E2.id 
WHERE E1.salary > E2.salary;

2.# Write your MySQL query statement below
DELETE p1 FROM Person AS p1,
    Person AS p2
    WHERE p1.id > p2.id
    AND p1.email = p2.email;

3. # Write your MySQL query statement below
SELECT Customers.name AS Customers
FROM Customers
LEFT JOIN Orders
ON Customers.id = orders.customerId 
WHERE orders.customerId IS NULL;

4.  Write your MySQL query statement below
UPDATE Salary
SET Sex = CASE Sex WHEN 'm' THEN 'f' ELSE 'm'
END;

5. # Write your MySQL query statement below
SELECT activity_date as day, COUNT(DISTINCT user_id) as active_users
FROM Activity
WHERE datediff('2019-07-27',activity_date)<30 
AND activity_date <= '2019-07-27' 
GROUP BY activity_date; 

6. # Write your MySQL query statement below
Select sell_date, count(distinct product) as num_sold, group_concat(distinct product) as products
From Activities
Group by sell_date
Order by sell_date;

7. # Write your MySQL query statement below
SELECT P1.product_id, P1.product_name
FROM Product P1, Sales S1
WHERE P1.product_id = S1.product_id
GROUP BY (P1.product_id)
HAVING MIN(sale_date) >= CAST("2019-01-01" AS DATE)  and MAX(sale_date) <= CAST("2019-03-31" AS DATE);