Key in MySQL are the fundamental elements for constructing a relationship between two tables. They are very useful in the maintenance of a relational database structure. The primary key is a unique or non-null key that uniquely identifies every record in a table or relation. Each database needs a unique identifier for every row of a table, and the primary key plays a vital role in identifying rows in the table uniquely. The primary key column can't store duplicate values. It is also called a minimal super key; therefore, we cannot specify more than one primary key in any relationship.
For example, we have a table named customer with attributes such as ID, Name, and City. Only the ID column can never contain duplicate and NULL values because each customer has a unique identification number. This feature helps to identify each record in the database uniquely. Hence, we can make the ID attribute a primary key.
In this article, we are going to cover the essential differences between Primary and Foreign Keys based on various parameters. Before making a comparison, we will discuss in brief these keys.
What is Foreign Key?
The foreign key is a group of one or more columns in a database to uniquely identify another database record in some other table to maintain the referential integrity. It is also known as the referencing key that establishes a relationship between two different tables in a database. A foreign key always matches the primary key column in another table. It means a foreign key column in one table refers to the primary key column of another table. A foreign key is beneficial in relational database normalization, especially when we need to access records from other tables.