Stored Procedures vs. Application Code: Choosing the Right Home for Your Business Logic

Here's a breakdown of both approaches with their pros and cons, illustrated with simple examples:

Business Logic in the Database (Stored Procedures):

Example:

CREATE OR REPLACE PROCEDURE calculate_discount(price IN NUMBER, customer_type IN VARCHAR2)
AS
  discount NUMBER;
BEGIN
  IF customer_type = 'VIP' THEN
    discount := price * 0.1;
  ELSE
    discount := price * 0.05;
  END IF;
  UPDATE orders SET discount = discount WHERE order_id = :order_id;
END;
/

Pros:

• Centralized logic: Ensures consistency and reduces redundancy as the logic resides in one place.
• Security: Database servers often offer robust security features to control access to procedures.
• Performance optimization: For complex calculations, stored procedures can sometimes outperform application code due to the database's optimized execution engine.

Cons:

• Vendor Lock-in: Stored procedures are specific to the database system (e.g., Oracle PL/SQL), making migration to other databases difficult.
• Limited functionality: Databases excel at storing and retrieving data, not complex logic branching or user interaction.
• Debugging and testing are harder: Stored procedures might require specialized tools and expertise to debug and test compared to application code.

Business Logic in the Application Layer:

def calculate_discount(price, customer_type):
  if customer_type == "VIP":
    discount = price * 0.1
  else:
    discount = price * 0.05
  return discount

# Apply discount in the application
order.discount = calculate_discount(order.price, order.customer_type)

• Portability: Logic written in general-purpose languages like Python is readily portable across different platforms and databases.
• Maintainability: Easier to understand, modify, and test compared to stored procedures.
• Flexibility: Applications can leverage various libraries and frameworks for complex logic and user interaction.

• Security: Requires proper security measures in the application layer to prevent unauthorized access or manipulation.
• Potential performance issues: Complex logic in the application might require optimization to avoid performance bottlenecks.

Related Issues and Solutions:

• Hybrid approach: Some developers advocate for a hybrid approach, placing simple validation rules in the database and complex logic in the application layer.
• Testing and documentation: Regardless of where logic resides, ensure proper testing and documentation to maintain code clarity and consistency.