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