DBMS Notes
HubUnit 1 — Introduction to DBMS & Entity-Relationship ModelAdvantages and Disadvantages of DBMSAggregation — Database Management SystemsCharacteristics of DBMSData IndependenceData ModelsDatabase Users and AdministratorsDBMS LanguagesER DiagramsEntity-Relationship (ER) ModelIntroduction to DBMSKeys in DBMSRelationships and CardinalitySchema and InstanceSpecialization and GeneralizationDBMS Unit 1 Summary - Database FundamentalsThree-Level Architecture (ANSI/SPARC Architecture)Weak Entity SetUnit 2 — Relational Model & SQLConstraints in SQLCursorsDCL and TCL CommandsDDL CommandsDML CommandsDomain Relational Calculus (DRC) - Complete TutorialFunctions and Stored ProceduresJoins in SQLNested Queries (Subqueries)Relational AlgebraRelational Calculus in Database Management SystemsRelational ModelSQL IntroductionDBMS Unit 2 Summary - SQL and Relational ModelTriggers in SQL — Database Management SystemsTuple Relational Calculus (TRC)Views in SQL — Database Management SystemsArmstrong\Boyce-Codd Normal Form (BCNF) — Database Management SystemsClosure of AttributesDependency PreservationFifth Normal Form (5NF)First Normal Form (1NF) - Database NormalizationFourth Normal Form (4NF)Functional DependencyLossless DecompositionMultivalued DependencyNormal Forms — OverviewNormalization — IntroductionSecond Normal Form (2NF) — Database Management SystemsUnit 3 Summary — NormalizationThird Normal Form (3NF) — Database Management SystemsUnit 4 — Transaction Management & Concurrency ControlACID PropertiesCheckpointsConcurrency Control & SerializabilityDeadlock in DBMSLock-Based Protocols & Two-Phase LockingLog-Based RecoveryRecovery SystemSerializabilityShadow PagingUnit 4 Summary — Transaction Management & Concurrency ControlTimestamp-Based ProtocolTransaction ManagementTransaction StatesTwo-Phase Locking (2PL)Unit 5 — Storage & IndexingB+ TreeB-TreeCost EstimationDynamic HashingFile OrganizationHashing TechniquesIndexing — IntroductionMulti-Level IndexingQuery Optimization — Database Management SystemsQuery ProcessingSingle-Level IndexingStatic HashingUnit 5 Summary — Storage & IndexingUnit 6 — Advanced Topics in DBMSBig Data and DBMSCloud DatabaseData MiningData WarehouseDatabase SecurityDistributed DatabaseDistributed Query ProcessingDistributed DBMS Architecture, Fragmentation & ReplicationMongoDB — IntroductionNoSQL DatabaseReplication in Distributed DatabasesUnit 6 Summary — Advanced Topics in DBMSViva Voce — DBMSImportant Viva Questions — DBMSInterview Questions — DBMSViva Answers — DBMSDBMS Multiple Choice Questions (MCQs)DBMS Lab Programs
Both functions and stored procedures are named, reusable blocks of SQL/PL-SQL code stored inside the database. They encapsulate business logic that can be...
Overview
Both functions and stored procedures are named, reusable blocks of SQL/PL-SQL code stored inside the database. They encapsulate business logic that can be executed repeatedly without rewriting the same statements. Think of them as the database equivalent of functions in a programming language — they accept inputs, perform processing, and return results.
The key difference is their intent: functions compute and return a single value (used inside expressions), while procedures execute complex operations that may modify data, return multiple outputs, and control transactions.
Stored Procedures
Basic Procedure (No Parameters)
sql example
DELIMITER //
CREATE PROCEDURE GetAllEmployees()
BEGIN
SELECT emp_id, name, salary, dept_id
FROM Employee
ORDER BY name;
END //
DELIMITER ;
-- Execute it
CALL GetAllEmployees();Procedure with IN Parameter
The IN parameter passes a value into the procedure (read-only inside the procedure):
sql example
DELIMITER //
CREATE PROCEDURE GetEmployeesByDept(IN p_dept_id INT)
BEGIN
SELECT emp_id, name, salary
FROM Employee
WHERE dept_id = p_dept_id
ORDER BY salary DESC;
END //
DELIMITER ;
-- Call with department ID 3
CALL GetEmployeesByDept(3);Procedure with OUT Parameter
The OUT parameter sends a value back to the caller:
sql example
DELIMITER //
CREATE PROCEDURE GetDeptStats(
IN p_dept_id INT,
OUT p_avg_sal DECIMAL(10,2),
OUT p_count INT,
OUT p_max_sal DECIMAL(10,2)
)
BEGIN
SELECT AVG(salary), COUNT(*), MAX(salary)
INTO p_avg_sal, p_count, p_max_sal
FROM Employee
WHERE dept_id = p_dept_id;
END //
DELIMITER ;
-- Call and retrieve output
CALL GetDeptStats(1, @avg, @cnt, @max);
SELECT @avg AS AvgSalary, @cnt AS HeadCount, @max AS MaxSalary;Procedure with INOUT Parameter
The INOUT parameter is both read and written — the value comes in, gets modified, and goes back:
sql example
DELIMITER //
CREATE PROCEDURE ApplyBonus(INOUT p_salary DECIMAL(10,2), IN p_percent DECIMAL(5,2))
BEGIN
SET p_salary = p_salary + (p_salary * p_percent / 100);
END //
DELIMITER ;
SET @sal = 75000;
CALL ApplyBonus(@sal, 10);
SELECT @sal; -- Returns 82500Procedure with Conditional Logic
sql example
DELIMITER //
CREATE PROCEDURE CategorizeSalary(IN p_emp_id INT, OUT p_category VARCHAR(20))
BEGIN
DECLARE v_salary DECIMAL(10,2);
SELECT salary INTO v_salary FROM Employee WHERE emp_id = p_emp_id;
IF v_salary >= 100000 THEN
SET p_category = 'Senior';
ELSEIF v_salary >= 60000 THEN
SET p_category = 'Mid-Level';
ELSE
SET p_category = 'Junior';
END IF;
END //
DELIMITER ;Procedure with Loop and Cursor
sql example
DELIMITER //
CREATE PROCEDURE GiveAnnualRaise(IN p_dept_id INT, IN p_percent DECIMAL(5,2))
BEGIN
DECLARE v_done INT DEFAULT FALSE;
DECLARE v_emp_id INT;
DECLARE emp_cursor CURSOR FOR
SELECT emp_id FROM Employee WHERE dept_id = p_dept_id;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET v_done = TRUE;
OPEN emp_cursor;
read_loop: LOOP
FETCH emp_cursor INTO v_emp_id;
IF v_done THEN LEAVE read_loop; END IF;
UPDATE Employee
SET salary = salary * (1 + p_percent / 100)
WHERE emp_id = v_emp_id;
END LOOP;
CLOSE emp_cursor;
END //
DELIMITER ;
-- Give all CS dept employees a 5% raise
CALL GiveAnnualRaise(1, 5.0);Functions
Scalar Function (Returns Single Value)
Example
DELIMITER //
CREATE FUNCTION CalculateBonus(p_salary DECIMAL(10,2), p_rating INT)
RETURNS DECIMAL(10,2)
DETERMINISTIC
BEGIN
DECLARE bonus DECIMAL(10,2);
CASE p_rating
WHEN 5 THEN SET bonus = p_salary * 0.20;
WHEN 4 THEN SET bonus = p_salary * 0.15;
WHEN 3 THEN SET bonus = p_salary * 0.10;
ELSE SET bonus = p_salary * 0.05;
END CASE;
RETURN bonus;
END //
DELIMITER ;
-- Use inside a query (unlike procedures!)
SELECT name, salary, CalculateBonus(salary, rating) AS bonus
FROM Employee
WHERE dept_id = 1;
Function for Data Formatting
sql example
DELIMITER //
CREATE FUNCTION FormatName(p_first VARCHAR(50), p_last VARCHAR(50))
RETURNS VARCHAR(110)
DETERMINISTIC
BEGIN
RETURN CONCAT(UPPER(LEFT(p_last, 1)), LOWER(SUBSTRING(p_last, 2)),
', ',
UPPER(LEFT(p_first, 1)), LOWER(SUBSTRING(p_first, 2)));
END //
DELIMITER ;
-- Use in SELECT
SELECT FormatName(first_name, last_name) AS formatted FROM Employee;
-- Output: "Smith, John"Function for Business Logic
sql example
DELIMITER //
CREATE FUNCTION GetTaxBracket(p_annual_income DECIMAL(12,2))
RETURNS VARCHAR(30)
DETERMINISTIC
BEGIN
IF p_annual_income <= 250000 THEN RETURN 'No Tax';
ELSEIF p_annual_income <= 500000 THEN RETURN '5% Bracket';
ELSEIF p_annual_income <= 1000000 THEN RETURN '20% Bracket';
ELSE RETURN '30% Bracket';
END IF;
END //
DELIMITER ;When to Use Procedures vs. Functions
| Scenario | Use |
|---|---|
| Calculate a derived value for SELECT | Function |
| Process multiple records, modify data | Procedure |
| Implement a business transaction (transfer money) | Procedure |
| Format/transform a column value | Function |
| Generate reports with multiple result sets | Procedure |
| Validate data before insert | Function (in CHECK or trigger) |
Advantages of Stored Procedures and Functions
- Performance: Precompiled execution plan — no re-parsing on each call
- Security: Grant EXECUTE without exposing table structure; prevents SQL injection
- Maintainability: Change logic in one place; all callers get the update
- Network efficiency: One CALL sends complex logic server-side instead of multiple round-trips
- Encapsulation: Business rules live in the database, not scattered across applications
Dropping and Modifying
sql example
-- Remove
DROP PROCEDURE IF EXISTS GetAllEmployees;
DROP FUNCTION IF EXISTS CalculateBonus;
-- Modify (MySQL requires DROP + CREATE; some DBMS support ALTER)
-- Oracle/PostgreSQL support CREATE OR REPLACE:
CREATE OR REPLACE FUNCTION CalculateBonus(...) ...Understanding functions and procedures is essential for building production-grade database applications where performance, security, and maintainability are paramount.
Exam Focus
Revise definitions, diagrams, examples, and short-answer points for Functions and Stored Procedures.
Interview Use
Prepare one clear explanation, one practical example, and one common mistake for this Database Management Systems (DBMS) topic.
Search Terms
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