What is the purpose of a check constraint in SQL?

A Check constraint is a constraint used to limit the range of values ​​in a column in a table. It can be used to restrict values ​​in a column to meet certain conditions, such as ensuring values ​​in a column must be greater than 0 or must be in a specific list. Check constraints can ensure the integrity and consistency of data, ensuring that the data in the table complies with the predefined rules. If a Check constraint is violated, the insert or update operation will fail.