March 8, 2023 By Matthew Rathbone *

SQL Server is a popular and powerful relational database management system. It provides a variety of constraints to help you enforce data integrity in your databases. However, sometimes you may want to remove a constraint because it’s no longer needed, or because it’s causing problems. In this post, we’ll show you how to drop a constraint in SQL Server.

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Understanding Constraints in SQL Server

Before we dive into how to drop a constraint, let’s take a quick look at what constraints are and what they do in SQL Server.

A constraint is a rule that restricts the values that can be entered into a column in a table. There are several types of constraints in SQL Server, including primary key, foreign key, unique, check, and default constraints.

Constraints help you ensure the accuracy and consistency of your data. For example, you can use a primary key constraint to ensure that each row in a table has a unique identifier, or a foreign key constraint to ensure that a value in one table corresponds to a value in another table.

Dropping a Constraint in SQL Server

To drop a constraint in SQL Server, you’ll need to use the ALTER TABLE statement. The basic syntax of this statement is as follows:

ALTER TABLE table_name DROP CONSTRAINT constraint_name;

Where table_name is the name of the table that the constraint is applied to, and constraint_name is the name of the constraint that you want to drop.

Here’s a simple example of how you can drop a constraint in SQL Server. Let’s say you have a table called Orders with a primary key constraint called PK_Orders. To drop this constraint, you would run the following SQL statement:


Once you run this statement, the primary key constraint on the Orders table will be removed.

It’s important to note that you can only drop constraints that have been created by you, or by someone with the appropriate permissions. If you try to drop a constraint that has been created by the system, you’ll receive an error message.


Dropping a constraint in SQL Server is a relatively simple process. All you need to do is use the ALTER TABLE statement with the DROP CONSTRAINT clause. With this knowledge, you should now be able to remove constraints that are no longer needed, or that are causing problems in your databases.

We hope this post has been helpful in showing you how to drop a constraint in SQL Server. If you have any questions or comments, please let us know in the comments section below.