{"id":272,"date":"2024-11-23T07:08:40","date_gmt":"2024-11-23T00:08:40","guid":{"rendered":"https:\/\/www.pgtutorial.com\/?page_id=272"},"modified":"2025-01-22T09:35:37","modified_gmt":"2025-01-22T02:35:37","slug":"postgresql-check-constraint","status":"publish","type":"page","link":"https:\/\/www.pgtutorial.com\/postgresql-tutorial\/postgresql-check-constraint\/","title":{"rendered":"PostgreSQL CHECK Constraint"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use PostgreSQL CHECK<\/code> constraint to ensure values in table columns meet a condition.<\/p>\n\n\n\n

Introduction to PostgreSQL CHECK constraint #<\/a><\/h2>\n\n\n\n

PostgreSQL CHECK<\/code> constraints maintain data integrity by ensuring that the value in a column must satisfy a Boolean expression.<\/p>\n\n\n\n

When a column has a CHECK<\/code><\/code> constraint, and you attempt to insert<\/a> or update<\/a> a value that causes the Boolean expression to be false, PostgreSQL issues a constraint violation and rejects the changes.<\/p>\n\n\n\n

CHECK<\/code> constraints can be helpful to enforce data integrity rules at the database level. They prevent invalid data from being inserted or update in table columns.<\/p>\n\n\n\n

For example, you can use the CHECK<\/code> constraint to prevent negative values from being inserted into the price<\/code> column of the products<\/code> table.<\/p>\n\n\n\n

Here’s the syntax of the CHECK<\/code><\/code> constraint:<\/p>\n\n\n

CREATE<\/span> TABLE<\/span> table_name<\/span> (\n\u00a0 \u00a0\u00a0column1 data_type CONSTRAINT<\/span> constraint_name<\/span> CHECK<\/span>(boolean_expression),\n\u00a0 \u00a0\u00a0...\n\n);<\/code><\/span>Code language:<\/span> PostgreSQL SQL dialect and PL\/pgSQL<\/span> (<\/span>pgsql<\/span>)<\/span><\/small><\/pre>\n\n\n
In this syntax:<\/p>\n\n\n\n