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. …

Aug 5, 2019 · This article demonstrates how to add a primary key to an existing table in SQL Server using Transact-SQL. A primary key is a column that has been configured as the unique …

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 …

Dec 12, 2025 · This tutorial guides you through the complete process of adding a primary key to an existing table using T-SQL and SQL Server Management Studio (SSMS), tailored for a …

May 13, 2025 · Learn to add a primary key to existing SQL tables with ALTER TABLE in SQL Server, MySQL, PostgreSQL, and Oracle.

Jun 28, 2024 · This tutorial covers SQL Primary Key definitions, rules, How to add a primary key to an existing table in SQL, interesting facts, and more with detailed examples.

This SQL tutorial explains how to create and drop a primary key in SQL with syntax and examples. What is a primary key in SQL? In SQL, a primary key is a single field or …

Jul 23, 2025 · PRIMARY KEY in SQL is a column (or group of columns) that uniquely identifies the records in that table. A primary key must contain unique values and can not have any …

Primary Key can be created in two ways in SQL Server: A primary key can be configured in the create table T-SQL script. Append CONSTRAINT statement at the end of all column …

Sep 22, 2025 · Wondering how to create a Primary Key in SQL? A Primary Key uniquely identifies each record in a table, ensuring data integrity. Continue reading to examine how to define a …