In a database management system, integrity constraints are rules that ensure the consistency and accuracy of data. There are several types of integrity constraints, including:
Primary Key Constraint: A primary key is a unique identifier that is used to identify each record in a table. This constraint ensures that there are no duplicate values in the primary key column. For example, in a customer table, the customer ID can be set as the primary key.
Unique Constraint: A unique constraint ensures that there are no duplicate values in a particular column, other than the primary key column. For example, in a customer table, the email address column can be set as a unique constraint to ensure that no two customers have the same email address.
Foreign Key Constraint: A foreign key is a column that refers to the primary key of another table. This constraint ensures that the values in the foreign key column correspond to the values in the primary key column of the other table. For example, in an order table, the customer ID column can be a foreign key that refers to the customer table's primary key.
Check Constraint: A check constraint ensures that the values in a column meet a specific condition. For example, in a student table, the age column can have a check constraint that the value should be between 18 and 30.
Not Null Constraint: A not null constraint ensures that a column cannot have a null value. For example, in an employee table, the employee ID column cannot be null.
These integrity constraints ensure the consistency and accuracy of data, which is crucial for maintaining the reliability of a database management system.
