a) Collection of Records
b) Collection of Keys
c) Collection of Tables
d) Collection of Fields
A foreign key is a column (or a set of columns) in one table that refers to the primary key of another table. It establishes a link between the two tables, ensuring data consistency and integrity.
Imagine this:
- You have a table called “Customers” with columns like “Customer ID”, “Name”, “Address”.
- You have another table called “Orders” with columns like “Order ID”, “Customer ID”, “Order Date”, “Total Amount”.
The “Customer ID” in the “Orders” table is a foreign key. It references the “Customer ID” in the “Customers” table. This means that every order must be associated with an existing customer.
Key points about foreign keys:
- It maintains referential integrity, ensuring that related data exists.
- It helps to normalize data by reducing redundancy.
- It allows you to retrieve related data efficiently through joins.
By using foreign keys, you create a structured and connected database where information can be easily managed and retrieved.