Integrity Constraints

Integrity constraints in a Database Management System (DBMS) are rules that ensure the accuracy and consistency of data within the database. These constraints enforce certain conditions on the data, preventing invalid or inconsistent data from being entered or manipulated. Integrity constraints are crucial for maintaining the quality and reliability of the database --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Types of Integrity Constraints Domain Integrity Definition: Ensures that all values in a column fall within a specific range or set of permissible values. Example: A column for age might require that all entries be between 0 and 120. This can be enforced using data types, CHECK constraints, and DEFAULT values. Purpose: Prevents invalid data from being entered into a column. Entity Integrity Definition: Ensures that each entity (row) in a table is unique and can be identified uniquely. This is typically enforced by the use of a primary key. Example: A table of employees must have a unique employee ID for each row, and this column cannot contain NULL values. Purpose: Guarantees that no duplicate rows exist in the table and that each row can be uniquely identified. Referential Integrity Definition: Ensures that a foreign key value in one table corresponds to a valid primary key value in another table. This maintains the relationship between tables. Example: If a table Orders has a foreign key CustomerID that references the Customers table, the CustomerID must exist in the Customers table. Purpose: Ensures that relationships between tables remain consistent and that references between tables are valid. Key Integrity Definition: Ensures that keys, such as primary keys and unique keys, are used correctly and consistently within the database. Example: A PRIMARY KEY constraint on a column ensures that all values in that column are unique and not NULL. A UNIQUE constraint ensures that all values in a column are unique but allows NULL values. Purpose: Maintains uniqueness of certain columns and ensures proper identification of rows. Unique Constraint Definition: Ensures that all the values in a column or a set of columns are unique across the database. Example: An email column in a users table might have a UNIQUE constraint to ensure no two users can have the same email address. Purpose: Prevents duplicate values in specified columns. Not Null Constraint Definition: Ensures that a column cannot have a NULL value. Example: A column for the date of birth in a person’s table might have a NOT NULL constraint to ensure that every person must have a date of birth entered. Purpose: Ensures that certain columns always contain data and are never left empty.





Importance of Integrity Constraints Data Consistency:

Integrity constraints ensure that the data stored in the database remains consistent and valid. Data Accuracy:

By enforcing rules, the DBMS prevents erroneous or invalid data from being entered. Data Integrity: Ensures that relationships between data are maintained, particularly with referential integrity, which prevents orphaned records. Reliability:

Enhances the trustworthiness of the database, as users can rely on the data being accurate and consistent.