Primary Key: A Primary Key in a database table is a field in the table that uniquely identifies every row or record present in the database table. Example: Students in Universities are assigned a unique registration number. Therefore, in a STUDENT database table, the attribute “reg_no” acts as primary key. Foreign Key: Foreign Key is a column in a relational database table which provides a relation between two tables. It provides a cross reference between tables by pointing to primary key of another table. Example: In STUDENT database table, the attribute “reg_no” acts as primary key and in COURSE database table in which the student selects his or her course, the same “reg_no” acts as foreign key for the STUDENT table. Entity Integrity: Entity Integrity is a mechanism that is used to protect primary keys in the database. Entity Integrity ensures the following properties for primary key: The primary key of one database table row must not match the primary key of any other row present in the table. No component of primary key must be null.

Question

8. Cash RegisterThis exercise assumes you have created the RetailItem class for Programming Exercise 5. Create a CashRegister class that can be used with the RetailItem class. The CashRegister class should be able to internally keep a list of RetailItem objects. The class should have the following methods: A method named purchase_item that accepts a RetailItem object as an argument. Each time the purchase_item method is called, the RetailItem object that is passed as an argument should be added to the list. A method named get_total that returns the total price of all the RetailItem objects stored in the CashRegister object’s internal list. A method named show_items that displays data about the RetailItem objects stored in the CashRegister object’s internal list. A method named clear that should clear the CashRegister object’s internal list. Demonstrate the CashRegister class in a program that allows the user to select several items for purchase. When the user is ready to check out, the…

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Question

Chapter 3, Problem 18P

Program Plan Intro

Primary Key:

A Primary Key in a database table is a field in the table that uniquely identifies every row or record present in the database table.

Example:

Students in Universities are assigned a unique registration number.

Therefore, in a STUDENT database table, the attribute “reg_no” acts as primary key.

Foreign Key:

Foreign Key is a column in a relational database table which provides a relation between two tables. It provides a cross reference between tables by pointing to primary key of another table.

Example:

In STUDENT database table, the attribute “reg_no” acts as primary key and in COURSE database table in which the student selects his or her course, the same “reg_no” acts as foreign key for the STUDENT table.

Entity Integrity:

Entity Integrity is a mechanism that is used to protect primary keys in the database. Entity Integrity ensures the following properties for primary key:

The primary key of one database table row must not match the primary key of any other row present in the table.

No component of primary key must be null.

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8. Cash RegisterThis exercise assumes you have created the RetailItem class for Programming Exercise 5. Create a CashRegister class that can be used with the RetailItem class. The CashRegister class should be able to internally keep a list of RetailItem objects. The class should have the following methods: A method named purchase_item that accepts a RetailItem object as an argument. Each time the purchase_item method is called, the RetailItem object that is passed as an argument should be added to the list. A method named get_total that returns the total price of all the RetailItem objects stored in the CashRegister object’s internal list. A method named show_items that displays data about the RetailItem objects stored in the CashRegister object’s internal list. A method named clear that should clear the CashRegister object’s internal list. Demonstrate the CashRegister class in a program that allows the user to select several items for purchase. When the user is ready to check out, the…

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