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. …

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 …

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.

May 15, 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 …

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 …

Jun 9, 2025 · Master all facets of the Primary Key in SQL: rules, properties and benefits. Learn how to create an SQL Primary key and master ways to use it on the table.

Aug 7, 2025 · What is an SQL Primary Key? An SQL primary key is a column or a set of columns that uniquely identifies each row in a table. This means that no two rows can have the same …

Here, the college_id column is the PRIMARY KEY. This means that the values of this column must be unique and it cannot contain NULL values. Note that the above code works in all …

This SQL tutorial explains how to create and drop a primary key in SQL with syntax and examples. In SQL, a primary key is a single field or combination of fields that uniquely defines …