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. …

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 …

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 …

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

Nov 18, 2025 · Creating a primary key in an existing table requires ALTER permission on the table. In Object Explorer, right-click the table to which you want to add a unique constraint, and …

The primary key constraint is specified at the time of creating a table, either through the CREATE TABLE statement or the ALTER TABLE statement. A primary key can be made up of one or …

We can create this Primary Key constraint using the Transact query and the Management Studio. Let us see how to create a Primary Key using a transact query and create a table statement.

What Is a Primary Key Constraint? A primary key constraint is a rule in SQL that ensures each row in a table has a unique, non-null identifier. It’s applied to one or more columns, called the …

Aug 7, 2025 · In this tutorial, I’ll walk you through an in-depth exploration of SQL primary keys, covering core principles, implementation methods, and optimization techniques. I’ll also cover …

The complete guide to SQL PRIMARY KEY. Learn the syntax, parameters, use cases and find practical examples in the Hightouch SQL Dictionary.