How is data integrity ensured in a database?

Data integrity in a database is ensured through several mechanisms:

• Constraints:

  • Primary Key — a unique identifier for a record.
  • Foreign Key — maintains referential integrity between tables.
  • Unique — guarantees the uniqueness of a value in a column.
  • Not Null — prohibits storing null values.

• Transactions:

  • Ensure atomicity of operations (ACID), so changes are either fully applied or not applied at all.

• Triggers and procedures:

  • Automatically check and enforce integrity rules when data is modified.

• Application-level validation:

  • Additional data validation before writing to the database.

These mechanisms together help prevent inconsistent or erroneous data in the database.