Primary Key vs Foreign Key in SQL

Hi !
Welcome to the new edition of Business Analytics Review !

Today we would be exploring SQL databases, focusing specifically on the concepts of Primary Keys and Foreign Keys. These fundamental components are essential for establishing relationships between tables and ensuring data integrity in relational databases .

Primary Key

• Unique Identifier: A primary key is a column (or a combination of columns) that uniquely identifies each row in a table.

• Non-Null: It cannot contain null values.

• One per Table: A table can have only one primary key.

• Purpose: Ensures data integrity by preventing duplicate records.

Example: Consider a Customers table with columns CustomerID, CustomerName, and City. CustomerID can be the primary key as it uniquely identifies each customer.

CREATE TABLE Customers (
    CustomerID INT PRIMARY KEY,
    CustomerName VARCHAR(255),
    City VARCHAR(255) 
    )