Jan 30, 2025 · In this article, we will explain the most common SQL constraints in detail, providing clear examples and explaining how to implement them effectively. What Are SQL Constraints?

Constraints can be column level or table level. Column level constraints apply to a column, and table level constraints apply to the whole table. The following constraints are commonly used in SQL: …

Sep 22, 2025 · Explore Key Constraints in SQL with practical examples, and understand how they ensure data integrity and prevent errors in relational databases.

Feb 8, 2023 · In this SQL tutorial, we’ll demonstrate examples for the types of constraints that can be created in Microsoft SQL Server. The T-SQL constraint code can be copied, pasted, and modified for …

To learn more, visit SQL UNIQUE Constraint. The PRIMARY KEY constraint is simply a combination of NOT NULL and UNIQUE constraints. It means that the column value is used to uniquely identify the …

Jul 19, 2025 · SQL Constraints are rules enforced on data columns in a database table. They help ensure the accuracy, consistency, and reliability of the data stored in a database.

SQL constraints are rules enforced on data columns in SQL Server databases. They ensure the accuracy and reliability of the data in the database. By restricting the type of data that can be stored …

Sep 11, 2025 · In this note we’ll discuss key constraints (PRIMARY KEY, UNIQUE), referential integrity (FOREIGN KEY), and column-level rules (NOT NULL, DEFAULT, CHECK). Tuples can have keys, …

SQL constraints are rules you apply to columns or tables that restrict the type of data that can be inserted. These constraints help enforce data integrity, which is the accuracy and consistency of data …