What are constraints in a Relational Database Management System (RDBMS)?

In a Relational Database Management System (RDBMS), constraints serve the vital purpose of enforcing data integrity automatically. This means that constraints are specific rules applied to columns in a database table that ensure the accuracy and reliability of the data being stored. They define conditions under which data can be inserted, updated, or deleted, thereby helping to maintain the quality of the database.

For instance, a common type of constraint is the primary key constraint, which ensures that each record in a table is unique and not null. This prevents situations where duplicate records can occur, which would compromise the integrity of the data. Other examples include foreign key constraints, which maintain the relationship between tables, and check constraints, which enforce specific conditions on the data being entered.

By utilizing constraints, an RDBMS can ensure that only valid data is entered, which is crucial for maintaining database reliability and consistency. This is how constraints play a fundamental role in protecting data integrity within relational databases.