Stored Procedures & Functions

Table of Contents

• Overview
• When to Use
• Quick Start
• Reference Guides
• Best Practices

Overview

Implement stored procedures, functions, and triggers for business logic, data validation, and performance optimization. Covers procedure design, error handling, and performance considerations.

When to Use

• Business logic encapsulation
• Complex multi-step operations
• Data validation and constraints
• Audit trail maintenance
• Performance optimization
• Code reusability across applications
• Trigger-based automation

Quick Start

PostgreSQL - Scalar Function:

-- Create function returning single value
CREATE OR REPLACE FUNCTION calculate_order_total(
  p_subtotal DECIMAL,
  p_tax_rate DECIMAL,
  p_shipping DECIMAL
)
RETURNS DECIMAL AS $$
BEGIN
  RETURN ROUND((p_subtotal * (1 + p_tax_rate) + p_shipping)::NUMERIC, 2);
END;
$$ LANGUAGE plpgsql IMMUTABLE;

-- Use in queries
SELECT id, subtotal, calculate_order_total(subtotal, 0.08, 10) as total
FROM orders;

-- Or in application code
SELECT * FROM orders
WHERE calculate_order_total(subtotal, 0.08, 10) > 100;

Reference Guides

Detailed implementations in the references/ directory:

Guide	Contents
Simple Functions	Simple Functions
Stored Procedures	Stored Procedures
Simple Procedures	Simple Procedures
Complex Procedures with Error Handling	Complex Procedures with Error Handling
PostgreSQL Triggers	PostgreSQL Triggers
MySQL Triggers	MySQL Triggers

Best Practices

✅ DO

• Follow established patterns and conventions
• Write clean, maintainable code
• Add appropriate documentation
• Test thoroughly before deploying

❌ DON'T

• Skip testing or validation
• Ignore error handling
• Hard-code configuration values