Difference Between Primary Key Foreign Key

This article will teach you the difference between a primary key and a foreign key this article will also teach you why both of these keys are important when it comes to the maintenance of a relational database structure.

Difference between primary key foreign key. Key differences between primary key and foreign key. The key difference between primary key and foreign key is the primary key is column which has n number of unique values and foreign key is key which behaves like primary key in parent table and a foreign key in child table primary key identify uniquely every row which can not be null. Both the primary key and foreign key are used in the relational database management systems rdbms where primary key is a uniquely identified field that can be used as a reference for relating the tables in the database system. However a foreign key in a table refers to the primary key of another table.

A primary key is a special key in a relational database that acts as a unique identifier for each record meaning it uniquely identifies each row record in a table and its value should be unique for each row of the table. The key difference between foreign key and primary key is that foreign key is a column or a set of columns that refer to a primary key or a candidate key of another table while primary key is a column or a set of columns that can be used to uniquely identify a row in a table. A column or a set of columns that can be used to identify or access a row or a set of rows in a database is called a key. A primary is a set of attributes a candidate key that distinctly identifies a record in a relation.

Database designing is one of the most important activity that should be done when maintaining and storing data. In sql server there are two keys primary key and foreign key which seems identical but actually both are different in features and behaviors. A primary key is used to ensure data in the specific column is unique. Difference between primary key and foreign key basics of primary key vs foreign key.

In this article i would like to share the key difference between primary key and foreign key. Primary key vs candidate key though primary key is selected from the candidate keys there exist some difference between the primary key and the other candidate keys which will be discussed in detail in this article. No primary key attributes can contain null values whereas a foreign key attribute can accept null value. A foreign key is a column or group of columns in a relational database table that provides a link between data in two tables.

It uniquely identifies a record in the relational database table. All the examples for this lesson are based on microsoft sql server management studio and the adventureworks2012 database. The difference between primary key unique key and foreign key is the most common interview question for net as well as sql developers. Primary key foreign key.