In order to understand the difference between a primary key and a foreign key, it is first important to understand what each term means. A primary key is a column or set of columns in a table that uniquely identifies each row in the table. A foreign key is a column or set of columns in one table that references the primary key of another table. In other words, the foreign key provides a link between two tables. Let’s take a look at an example to make things clearer.
What is Primary Key?
The primary key is an essential element of data storage, as it uniquely identifies each row of the database table. Primary keys provide the basis by which each record can be found and sorted within a database. Unlike other keys, primary keys are not optional – they must be present in order to identify a record from any other record in the table.
Primary keys cannot contain null values or duplicates, which makes them an incredibly powerful tool for retrieving precise information from the database quickly and accurately. Primary keys are one of the most crucial components needed to organize, manage, and secure any type of data storage system.
What is Foreign Key?
Foreign Key is a type of column in a relational database. It allows the data within one table to be related to the data of another table – for example when two or more tables need to be linked together in order to populate their respective entries. Foreign Keys can help maintain data integrity by giving the database user a way to ensure that multiple tables accurately reflect their interrelated values. Foreign Keys are often used by software developers in order to control and simplify complex joins between different types of data, which helps make sure that only valid connections are being made.
Difference between Primary Key and Foreign Key
The primary Key and Foreign Key are two important elements of database architecture.
- Primary Keys maintain the uniqueness of each record in the database by serving as an identifier for each row in a table.
- In contrast, a Foreign Key makes sure that all chosen columns exist within two or more different tables.
- It further protects the data integrity by requiring the foreign key must already be present for it to be used within another table.
Primary Keys and Foreign Keys are critical components for establishing consistency and structure of databases, making them essential building blocks to understanding how a database works.
Conclusion
A primary key is a column (or set of columns) that uniquely identifies each row in a table. A foreign key is a column (or set of columns) in one table that references the primary key of another table. In other words, the foreign key provides a link between two tables. When you create relationships between tables, you use foreign keys to identify which records in one table are related to which records in another table. Without foreign keys, your database would be unable to keep track of the relationships between data in different tables. Primary and foreign keys are both essential for creating and maintaining accurate database relationships.
