Chapter 23, Problem 15RE

Explanation of Solution

Consider the following:

The below SQL statement that compute and finds the total cost of all line items in invoice number 11731:

/* Display the total cost of lineitem products */

SELECT SUM(Product.Price * LineItem.Quantity)

FROM Product, LineItem

WHERE LineItem.Invoice_Number = 11731

AND LineItem.Product_Code = Product.Product_Code

Explanation:

• The above “SELECT” statement that calculate and returns the “SUM(Product.Price * LineItem.Quantity)” columns from the “Product” and “LineItem” tables where “LineItem.Invoice_Number” is equal to “11731” and “LineItem.Product_Code” is equal to “Product.Product_Code”.
  • “SUM(Product.Price * LineItem.Quantity)” – It  finds and returns the total cost of all line items product value related to the given invoice number “11731”.
    • “SUM” – It is a predefined function used to calculate the sum of a field.
    • “Product...