How does a database enforce data integrity?

A database enforces data integrity through constraints, triggers, and transactions that ensure accuracy and consistency of data.

Data integrity is a fundamental aspect of storing information in databases. It ensures that the data entered into the database is accurate, reliable and consistent over its entire lifecycle. There are several ways a database management system (DBMS) enforces data integrity, including the use of constraints, triggers, and transactions.

Constraints are rules that are applied to fields in a database table. They limit the type of data that can be stored in a field, ensuring that the data is valid and reliable. For example, a constraint might specify that a field must contain a unique value, or that it cannot be left empty (NULL). Constraints can also be used to establish relationships between tables, such as foreign key constraints, which ensure that the data in a field matches data in a different table.

Triggers are another way that databases enforce data integrity. A trigger is a type of stored procedure that automatically executes, or fires, in response to a specific event, such as inserting, updating, or deleting data in a table. Triggers can be used to enforce business rules and to maintain complex integrity constraints that cannot be enforced through the use of simple constraints. For example, a trigger might be used to automatically update a summary field whenever a record is added, modified, or deleted.

Transactions are a third way that databases enforce data integrity. A transaction is a sequence of one or more operations that are executed as a single unit of work. If all the operations in the transaction are completed successfully, the transaction is committed and the changes are made permanent. If an error occurs during any operation in the transaction, the entire transaction is rolled back, and the database is returned to its previous state. This ensures that the database remains in a consistent state, even in the event of a system failure or error.

In conclusion, data integrity is a critical aspect of database management. By using constraints, triggers, and transactions, a DBMS can ensure that the data stored in a database is accurate, reliable, and consistent.