UNIQUE KEY IN SQL | SQL UNIQUE Constraint | SQL Server Tutorial for Beginners in Hindi|2024
UNIQUE KEY IN SQL IN HINDI
In this tutorial, you'll delve into the realm of SQL to understand the significance of unique keys.
We'll explore their syntax, providing clear examples to illustrate their usage and functionality.
Unique keys are fundamental in database management, ensuring that each record within a table possesses a distinct identifier.
Through comprehensive explanations and practical demonstrations, you'll grasp how unique keys enforce data integrity and maintain the integrity of your database.
By the end of this tutorial, you'll emerge with a solid understanding of unique keys in SQL, equipped with the knowledge to implement them effectively in your own projects.
In this tutorial, we'll explore unique keys in SQL through hands-on examples, starting with creating a table.
Unique Key in SQL
A unique key is a set of one or more than one fields/columns of a table that uniquely identify a record in a database table.
You can say that it is little like primary key but it can accept only one null value and it cannot have duplicate values.
The unique key and primary key both provide a guarantee for uniqueness for a column or a set of columns.
There is an automatically defined unique key constraint within a primary key constraint.
There may be many unique key constraints for one table, but only one PRIMARY KEY constraint for one table.
CREATE TABLE students
(
S_Id int NOT NULL UNIQUE,
LastName varchar (255) NOT NULL,
FirstName varchar (255),
City varchar (255)
)