The CHECK constraint in SQL is used to enforce domain integrity by ensuring that all values in a column or a set of columns satisfy a specified Boolean expression. When a CHECK constraint is defined on a column, the database management system (DBMS) validates any new or updated data against this expression. If the expression evaluates to FALSE, the INSERT or UPDATE operation is rejected. This directly limits the set of permissible values that can be stored in the column, enforcing a specific business rule or data validation logic.

This is a "True or False" question. The statement is factually correct according to standard SQL definitions and implementations. Therefore, selecting "False" would be incorrect as it contradicts the fundamental purpose of the CHECK constraint. Other constraints serve different purposes: NOT NULL ensures a value is present, UNIQUE ensures no duplicate values, and FOREIGN KEY ensures referential integrity, but CHECK is specifically for validating the value itself against a condition.

1. PostgreSQL 16 Documentation

Chapter 5. Data Definition

Section 5.4.5. Check Constraints:

"A check constraint specifies that the values in a column must satisfy a Boolean (truth-value) expression. The expression should return true or unknown for the constraint to succeed. ... A check constraint specified as a column constraint should only reference that column's value

while a check constraint specified as a table constraint can reference multiple columns."

This source confirms that the core function is to ensure column values satisfy a specific expression

thereby limiting them.

2. Snowflake Documentation

SQL Reference

CREATE TABLE

tableconstraint:

Under the definition of constraints

it lists CHECK ( ). The purpose of constraints is to "ensure data integrity". The CHECK constraint achieves this by evaluating the expression for each row

which limits the values to only those for which the expression is not false.

3. Stanford University

CS 145: Introduction to Databases

Lecture Notes on SQL:

In the section covering Data Definition Language (DDL) and constraints

the CHECK constraint is defined as: CHECK . The notes explain that this constraint ensures that attribute values must satisfy the specified condition. For example

CHECK (rating >= 1 AND rating <= 10) limits the rating column to integers between 1 and 10

inclusive. This is a direct example of limiting values in a column.