Data Integrity Considerations
In SQL database management systems, data integrity refers to the accuracy, consistency, flexibility, and reliability of the data existing in the database tables. Managing database data integrity is crucial for maintaining valid and meaningful data record information in the database tables. Data integrity features are very important for database users; data integrity ensures that the existing database data is reliable and useful, it reduces data redundancy in the database, and prevents false or unnecessary data information from being entered or stored in the database management system.
Types of Data Integrity in SQL Database Management Systems.
The data integrity concept in SQL database management systems has multiple types, where each type indicates a focus on multiple aspects of the accuracy and consistency of the database data.
Database Entity Integrity.
Entity integrity in a database table ensures that every table row created by any database user is unique and that the table row field can be validated by a unique key, such as a primary key. Entity integrity in a database table ensures that the inserted record data in each table is unique, thereby preventing repetition and ambiguity in the existing database table records.
Database Referential Integrity.
Referential integrity in a database table ensures that the table relationships between existing database tables are regularly maintained. When a table x in the database references another table y, for example, through a foreign key, referential integrity ensures that the foreign key in the child table properly matches a valid primary key in the parent table in the two existing database tables.
Database Domain Integrity.
Domain integrity in a database table ensures that the data values in the database table are valid according to a defined set of pre-defined rules for each column or domain. This includes applying database table data types, data ranges, and estimated data values to the process, ensuring that only valid and related data is stored in each table column.
Database User-Defined Integrity.
User-defined integrity in database tables includes applying commercial rules or user-created custom blocks or restrictions that ensure the database data is designed and developed according to specific user needs in the existing database. This involves checking or analysing complex conditions or calculations of database data that are uniquely compatible with a particular organization, company, or application.
Main Concepts for Maintaining Data Integrity Processes in Database Management Systems.
Primary Key Constraints Concept.
Primary keys in any user-created table uniquely identify or validate each table entry data record in the table. Each database table record must have a unique, non-null value.
Example of Primary Key Constraints Concept.
Here, in the employee table, we can set the employe_id column as the primary key, ensuring that each employee has a unique identifier data information.
CREATE TABLE employe (
employe_id INT PRIMARY KEY,
first_name VARCHAR(70),
last_name VARCHAR(70),
birth_date DATE
);
Primary Key Constraints Explanation.
Here, the primary key in the user-created table ensures that each table record data information in the designed table is unique and easily identifiable.
Foreign Key Constraints Concept.
Foreign keys in any user-created table maintain referential integrity in the existing database table by ensuring that the relationship between two different database tables is valid. The link between two different tables is indicated by linking a foreign key in a child table to a primary key in a parent table.
Example of Foreign Key Constraints Concept.
Here, in the `courses` table, the `student_id` column can be defined as a foreign key, referencing the `student_id` in the `students` table.
CREATE TABLE courses (
course_id INT PRIMARY KEY,
course_name VARCHAR(130),
student_id INT,
FOREIGN KEY (student_id) REFERENCES students(student_id)
);
Foreign Key Constraints Concept Explanation.
In this example, a foreign key prevents a record in the `courses` table from referencing a student who does not exist in the `students` table, thus ensuring data consistency across the database tables.
Unique Constraint Concept.
A unique constraint in any user-created table ensures that all data values in a table column or a combination of multiple columns are unique within the table. It’s a concept similar to a primary key, but it allows the database user to handle NULL values.
CREATE TABLE employee (
employee_id INT PRIMARY KEY,
emp_age INT,
email VARCHAR(100) UNIQUE
);
Unique Constraint Concept Explanation.
A unique constraint in a database table ensures that no duplicate email addresses are inserted into the existing employee table, which is essential for the validity of each unique user.
Check Constraint Concept.
A check constraint in a database table ensures that the data values inserted into a column meet certain criteria or conditions. This helps maintain domain integrity by applying rules to the valid data types and data ranges in the database table.
CREATE TABLE employe (
employe_id INT PRIMARY KEY,
emp_age INT,
CHECK (emp_age >= 21 AND emp_age <= 70)
);
Check Constraint Concept Explanation.
The check constraint in the database table ensures that only employee ages within the defined age range (21 to 70) are considered valid in the emp_age column.
NOT NULL Constraint Concept.
A NOT NULL constraint in a database table ensures that a table column cannot contain any NULL values. This is mostly used for table columns that should always contain data information.
CREATE TABLE employe (
employee_id INT PRIMARY KEY,
first_name VARCHAR(100) NOT NULL,
last_name VARCHAR(900) NOT NULL
);
NOT NULL Constraint Concept Explanation.
In the database table, the employee first_name and last_name table columns are defined as NOT NULL, meaning these table columns cannot be left empty, ensuring that every employee has a complete first and last name entered.
Default Value Concept.
A default value in a database table specifies that if no value is defined for a table column, the table column will use a predefined default value. This feature helps database users maintain database insert consistency when adding new table rows without having to specify every value.
CREATE TABLE product (
product_id INT PRIMARY KEY,
prod_name VARCHAR(140),
stock_inventory INT DEFAULT 0
);
Default Value Concept Explanation.
Here, if no stock_inventory value is provided by the database user, it will automatically be set to 0, ensuring that the column always has a consistent value, even if no data is explicitly provided for that column.
