Integrity constraints are rules or conditions that are defined and enforced on a database, in order to maintain data integrity and consistency. These constraints act as safeguards to ensure that data stored in the database meets certain criteria or conditions, preventing any inconsistent or invalid data from being inserted, updated, or deleted.
Integrity constraints can be divided into various types:
1. Domain constraints: These constraints define the allowed values for a particular attribute in a database table. For example, a domain constraint on a "gender" attribute may allow only two values - "male" or "female".
2. Key constraints: These constraints ensure that each record in a table has a unique identifier or key value. It can be a primary key constraint, which enforces uniqueness and non-nullability of a primary key attribute, or a unique key constraint, which enforces uniqueness on a non-primary key attribute.
3. Referential integrity constraints: These constraints maintain the consistency between related tables. For example, a foreign key constraint ensures that a value in a column of one table matches a value in the primary key column of another related table.
4. Entity integrity constraints: These constraints govern the primary key attribute(s) of a table, ensuring that it is unique and non-null.
5. Check constraints: These constraints validate the values that are entered or updated in a column against a predefined condition or expression. For example, a check constraint can restrict the age column to accept values between 18 and 65.
By enforcing these integrity constraints, databases can prevent data inconsistencies, maintain data accuracy and validity, and enhance the overall reliability and quality of the data stored within.
Describe Integrity Constraints.
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Define and Describe different types of Integrity Constraints.
1. Domain Constraints: Domain constraints define the permissible values for an attribute in a database table. They ensure that data entered into a column adheres to a predefined set of values. For example, a domain constraint on a "color" attribute may specify that the allowed values are "red," "blue," or "green," and any attempt to insert a different value would be rejected.
2. Key Constraints: Key constraints ensure the uniqueness and non-nullability of a primary key attribute in a table. A primary key constraint enforces that each record in a table has a unique identifier. It prevents duplicate or null values in the primary key column. Unique key constraints function similarly but are applied to non-primary key attributes.
3. Referential Integrity Constraints: Referential integrity constraints enforce the consistency and relationships between related tables. They are based on foreign key and primary key relationships. For example, a referential integrity constraint ensures that a value in a foreign key column matches a value in the referenced primary key column of another table. It prevents orphaned records and maintains data integrity in relational databases.
4. Entity Integrity Constraints: Entity integrity constraints govern the primary key attribute(s) of a table. They ensure that the primary key is unique and non-null for each record in the table. These constraints help maintain the uniqueness and identity of individual records.
5. Check Constraints: Check constraints validate the values entered or updated in a column against a predefined condition or expression. They define a logical condition that must be met for the data to be considered valid. For example, a check constraint can restrict the age column to accept values between 18 and 65, preventing the entry of invalid ages.
By utilizing these different types of integrity constraints, databases can ensure that the data stored within is accurate, consistent, and conforms to predefined rules and relationships. They help maintain data integrity and prevent the introduction of errors or inconsistencies into the database.
2. Key Constraints: Key constraints ensure the uniqueness and non-nullability of a primary key attribute in a table. A primary key constraint enforces that each record in a table has a unique identifier. It prevents duplicate or null values in the primary key column. Unique key constraints function similarly but are applied to non-primary key attributes.
3. Referential Integrity Constraints: Referential integrity constraints enforce the consistency and relationships between related tables. They are based on foreign key and primary key relationships. For example, a referential integrity constraint ensures that a value in a foreign key column matches a value in the referenced primary key column of another table. It prevents orphaned records and maintains data integrity in relational databases.
4. Entity Integrity Constraints: Entity integrity constraints govern the primary key attribute(s) of a table. They ensure that the primary key is unique and non-null for each record in the table. These constraints help maintain the uniqueness and identity of individual records.
5. Check Constraints: Check constraints validate the values entered or updated in a column against a predefined condition or expression. They define a logical condition that must be met for the data to be considered valid. For example, a check constraint can restrict the age column to accept values between 18 and 65, preventing the entry of invalid ages.
By utilizing these different types of integrity constraints, databases can ensure that the data stored within is accurate, consistent, and conforms to predefined rules and relationships. They help maintain data integrity and prevent the introduction of errors or inconsistencies into the database.
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