Database constraints are rules applied to table columns to ensure the accuracy, integrity, and consistency of data. They prevent invalid or unintended modifications to the database. Here are some common types of constraints: Types of Constraints: Primary Key – Ensures that a column (or set of columns) has unique values and cannot be NULL. Foreign Key – Enforces referential integrity by linking a column to another table’s primary key. Unique Constraint – Guarantees that all values in a column are distinct and Not Null – Prevents NULL values in a column. Check Constraint – Defines conditions that data must meet (e.g., age >= 18). Default Constraint – Provides a default value when none is specified. Why Constraints Are Important: Data Integrity – Constraints prevent incorrect or inconsistent data entry. Referential Integrity – Foreign keys ensure relationships between tables remain valid. Error Prevention – Helps detect and avoid mistakes before they affect the database. ...
