SQL PRIMARY KEY Constraint The PRIMARY KEY constraint is used to uniquely identify each record in a table. Primary keys must contain unique values, and cannot contain NULL values. Each table …

In this tutorial, you will learn how to use the SQL PRIMARY KEY constraint to add a primary key to the table.

Jul 23, 2025 · The PRIMARY KEY constraint in SQL is one of the most important constraints used to ensure data integrity in a database table. A primary key uniquely identifies each record in a table, …

Aug 6, 2025 · A primary key is a column in a database table that uniquely identifies each row. That means no two rows can have the same value in this column, and it can’t be left empty.

What is a primary key? A primary key is a column or columns in a database table with values that uniquely identify each row or record. For example, an employee ID column could be a primary key in …

Nov 18, 2025 · You can define a primary key in the SQL Server Database Engine by using SQL Server Management Studio or Transact-SQL. Creating a primary key automatically creates a corresponding …

Aug 7, 2025 · Understand what an SQL primary key is and its function in database relationships and query performance in this technical tutorial.

Every well-designed SQL table includes a primary key, whether it's a single column or a combination of multiple columns. This guide walks through how to define, use, and optimize primary key SQL …

The PRIMARY KEY constraint in SQL is a combination of NOT NULL and UNIQUE constraints and is used to uniquely identify the row. In this tutorial, you will learn about the PRIMARY KEY constraint in …

Mar 3, 2024 · At its core, a primary key is a unique identifier for each record in a SQL database table. This means no two rows can have the same value in the primary key column, ensuring that each …