How does sql allow implementation of the entity integrity and referencial integrity constraints?

SQL enforces entity integrity by requiring that primary key columns contain unique values and cannot be null, ensuring that each record in a table is distinct and identifiable. Referential integrity is maintained through the use of foreign keys, which establish a link between tables by ensuring that a foreign key value in one table corresponds to a primary key value in another. If a foreign key constraint is violated, such as by attempting to insert a non-existent reference, SQL will reject the operation, thus preserving data consistency across related tables. These constraints help maintain the accuracy and reliability of the database.