Please explain in detail why you chose each answer:

No written work.

16. What does the following command result? Select c.order Number, sum (priceEach) as total from orders c, orderdetails o where c.orderNumber = o.orderNumber Group by c.orderNumber 17. What does the following command result? SELECT YEAR(orderDate) AS year, SUM(quantityOrdered * priceEach) AS total FROM orders INNER JOIN orderdetails USING (orderNumber) WHERE status = 'Shipped GROUP BY YEAR(order Date); 18. What does the following command result? SELECT lastname, firstname, jobtitle, FROM employees WHERE jobtitle = 'Sales Rep' 19. Which of the following prevent duplicates of records? a. Unique Index b. Not Null c. Unique Data Type d. Binary Column 20. What is Float number? a. It includes a whole and decimal numbers (with 4 digits after the decimal point) b. It includes only decimal numbers (with 4 digits after the decimal point) C. It includes only a whole d. It includes all kinds of numbers and characters 21. Which data type should have a field "Course Number" in courses table? a INT b. VARCHAR C. FLOAT d. DECIMAL