SQL Server Interview Question #15

What is a primary key?

SQL Server Fundamentals Junior Beginner

Detailed Explanation

A primary key is a constraint that uniquely identifies each row in a table. Primary-key values must be unique and cannot be NULL.

A table can have only one primary-key constraint, but the primary key can contain more than one column; this is called a composite primary key.

Code Example

CREATE TABLE Customers
(
    Id INT PRIMARY KEY,
    Name NVARCHAR(100) NOT NULL
);