SQL PRIMARY KEY Constraint - W3Schools.com
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. …
SQL Primary Key
In this tutorial, you will learn how to use the SQL PRIMARY KEY constraint to add a primary key to the table.
What is a primary key? - IBM
A primary key is a column or columns in a database table with values that uniquely identify each row or record.
SQL PRIMARY KEY Constraint - GeeksforGeeks
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 …
What Is a Primary Key in SQL? Learn with Examples
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.
Primary and foreign key constraints - SQL Server
Feb 4, 2025 · This column, or columns, is called the primary key (PK) of the table and enforces the entity integrity of the table. Because primary key constraints guarantee unique data, …
SQL Primary Key: A Comprehensive Technical Tutorial - DataCamp
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 …
How to Use PRIMARY KEY in SQL - SQL Knowledge Center
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 …
SQL Primary Key: Purpose, Syntax, and Best Practices
What Is a Primary Key in SQL? A primary key in SQL is a column or set of columns whose values uniquely identify every row in a table. The database engine enforces two key rules on this …
Primary Key Constraint in SQL: Ensuring Unique and Reliable Data
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 …