Full Answer Section

Example:

Consider a database with two tables:

• Customers table: This table stores information about customers, such as customer ID, name, and address. The primary key of this table is the customer ID column.
• Orders table: This table stores information about customer orders, such as order ID, customer ID, and order date. The foreign key in this table is the customer ID column, which references the customer ID column in the Customers table.

Entity integrity in the Customers table would be ensured by having a unique customer ID for each customer. Referential integrity in the Orders table would be ensured by requiring that all customer ID values in the Orders table reference a valid customer ID value in the Customers table.

Why are entity integrity and referential integrity important?

Entity integrity and referential integrity are important because they help to ensure the accuracy and consistency of data in a database. Entity integrity ensures that each row in a table uniquely identifies a single entity, which prevents duplicate data from being entered into the database. Referential integrity ensures that all foreign key values in a table reference a valid primary key value in another table, which prevents orphaned records from being created.

Application example:

Consider a database used by an online retailer. The database would have tables to store information about customers, products, and orders. Entity integrity would be important in ensuring that each customer has a unique customer ID and that each product has a unique product ID. Referential integrity would be important in ensuring that all order IDs in the Orders table reference a valid customer ID in the Customers table and that all product IDs in the Orders table reference a valid product ID in the Products table.

Without entity integrity and referential integrity, the database could contain inaccurate and inconsistent data. For example, if entity integrity was not enforced, there could be multiple rows in the Customers table with the same customer ID. This could lead to duplicate orders being placed for the same customer. If referential integrity was not enforced, there could be rows in the Orders table with customer IDs that do not exist in the Customers table. This could lead to orphaned orders, which are orders that cannot be associated with a customer.

Entity integrity and referential integrity are essential for maintaining the accuracy and consistency of data in a database.