Constraints are kind of restrictions that are applied to the database or on the domain of an attribute. For example an integer attribute is restricted from 1-10 and not more than that. They provide the way to implement the business logic and the rules in database. In database it can be implemented in the form of check constraints that checks for the rules that haven’t been followed by the programmer. Constraint also used to restrict the data that can be stored in the relations. Domain constraint can be applied to check the domain functionality and keep it safe..