Integrity Constraints explain everything in it It's very useful

1. Integrity Constraints
Submitted by:
Fatima amir 22011556-010
Dilbaz sultan 22011556-012
Kinza shahzadi 22011556-054
Instructor :
Miss Sania Azhar

2. Integrity Constraints
 it's a core concept in database management systems (DBMS).
 They are rules enforced on data in a database to ensure its
• accuracy
• consistency
• Reliability
These are enforced automatically by the DBMS (like MySQL, PostgreSQL,
Oracle, etc.).

3. Types of Integrity Constraints
 Entity Integrity
 Referential Integrity
 Domain Integrity
 User-Defined Integrity

4. Entity Integrity
 Primary Key constraint
 Primary Key is a special column
 Ensures each row is uniquely identifiable
 It can’t be empty (NULL) and must be unique for every row.
 ID is the Primary Key
ID NAME
1
2
3
Alice
Bob
Charlie

5. A Student table in a school database:
 CREATE TABLE Student (
 StudentID INT PRIMARY KEY,
 Name VARCHAR(100),
 );
StudentID uniquely identifies each student
No two students can have the same StudentID
Every student must have one
Maintains data reliability and accuracy

6. Referential Integrity
 Ensures relationships between tables remain consistent
 Enforced using Foreign Keys
CREATE TABLE Department (
DeptID INT PRIMARY KEY,
DeptName VARCHAR(100)
);
CREATE TABLE Employee (
EmpID INT PRIMARY KEY,
Name VARCHAR(100),
DeptID INT,
FOREIGN KEY (DeptID) REFERENCES Department(DeptID)
);
Employee.DeptID must match a DeptID in Department
Keeps data across tables linked and accurate

7. Domain Integrity
 Ensures that each column contains only valid data
 Defines a “domain” or allowed set of values for a column
Data types (e.g., INT, VARCHAR, DATE)
CHECK constraints (e.g., Salary > 0)
Default values (e.g., status = ‘Active’)
CREATE TABLE Product (
ProductID INT PRIMARY KEY,
Price DECIMAL(10,2) CHECK (Price > 0),
Status VARCHAR(10) DEFAULT 'Available'
);
improves data quality and reliability

8. User-Defined Integrity
 Rules that are specific to the business or application
 Not covered by default system constraints (like PK or FK)
Enforce by:
 Using CHECK constraints
CREATE TABLE Employee (
EmpID INT PRIMARY KEY,
Name VARCHAR(100),
Salary DECIMAL(10,2) CHECK (Salary > 0)
);
 Helps maintain meaningful and valid data

9. Constraints in SQL
Constraints :
are rules applied to columns or tables in a database to ensure that the
data stored is accurate, consistent, and valid.
Purpose of Constraints:
To restrict the type of data that can be inserted into the
database.
To enforce business rules and maintain data integrity

10. Types of Constraints:
 Primary Key: Uniquely identifies each row in a table.
 Foreign Key: Ensures the relationship between two tables is valid.
 Check: Validates that data meets specific conditions (e.g., salary > 0).
 Not Null: Ensures that a column cannot have NULL values.
 Unique: Ensures all values in a column are unique.
SQL code snippets:
CREATE TABLE Employee (
ID INT PRIMARY KEY,
Name VARCHAR(100),
DepartmentID INT,
FOREIGN KEY (DepartmentID) REFERENCES Department(ID),
CHECK (Salary > 0)
);

11. Primary Key constraints
 Ensures unique identification for each row in a table.
 Cannot be NULL.
CREATE TABLE Employee (
ID INT PRIMARY KEY,
Name VARCHAR(100)
);

12. Foreign Key
 Links one table to another.
 Ensures data integrity by matching values to a primary key in another table.
 Example:
CREATE TABLE Employee (
EmpID INT PRIMARY KEY,
DeptID INT,
FOREIGN KEY (DeptID) REFERENCES Department(DeptID)
);

13. Unique constraints
 ensures all values in a column are unique.
 Example:
CREATE TABLE User (
UserID INT PRIMARY KEY,
Email VARCHAR(100) UNIQUE
);

14. Check constraints
 Validates data against a condition (e.g., positive salary).
 Example:
CREATE TABLE Employee (
ID INT PRIMARY KEY,
Salary DECIMAL(10, 2) CHECK (Salary > 0)
);

15. Constraints Matter
 Prevents data anomalies
 Improves data quality
 Reduces bugs in applications

16. Real-Life Applications of Integrity
Constraints:
 Integrity constraints aren’t just theory
 they help run the real world by protecting important data in many systems.
1. Banking Systems
Constraint: Balance cannot go below zero.
Why?
Prevents overdrafts unless allowed(only if overdraft protection is
enabled), protects customer accounts.
CHECK (Balance >= 0)

17. why is it important?
 It prevents errors or fraud, like someone accidentally or purposely trying to
take out more money than they have.
 It keeps the bank’s records safe and accurate, protecting both the
customer and the bank.

18. E_commerce
customer Table
 Imagine an online shopping system where:
 Every order must be placed by a valid customer
 Every product must have valid stock
 Prices and quantities must be logical
customerID Name Email
1
2
Alice
Bob
alice@gmai
l.com
bob@gmail
.com

19. Product Table
productID productname stock price
112
113
Keyboard
mouse
5
0
1000
500
Constraints:
•Stock >= 0 (Check Constraint)
•Price > 0 (Check Constraint)
•ProductID is Primary Key

20. OrderID CustomerID ProductID Quantity TotalAmount
201
202
1
2
101
102
1
1
1000
500
Foreign Key Constraints:
CustomerID must exist in Customer Table
ProductID must exist in Product Table
Check Constraint:
Quantity > 0
Order Table

21. E-commerce Platforms
Constraint: Stock quantity cannot be negative.
Why?
Ensures you don’t sell products you don’t have.
Example:
CHECK (Stock >= 0)
Important :
Prevents overselling
maintain accurate inventory levels.
Protects customer trust

22. Example Use in SQL:
 CREATE TABLE Product (
 ProductID INT PRIMARY KEY,
 ProductName VARCHAR(100),
 Stock INT CHECK (Stock >= 0)
 );
If someone tries to update Stock to -1, the database will reject the operation to keep the
data valid.

23. Best Practices
 Always define necessary constraints
 Don't overuse constraints that limit flexibility
 Test constraint rules carefully

24. Summary
 Ensure Consistency
 Avoid Logical Errors
 Support Business Rules
 Help in Decision-Making
 Build Trust

25. Questions
 Thank You!
 Any questions?