In real enterprise projects, developers often get confused about when to use a View, when to write a Stored Procedure, and when to use a Function. On paper, the definitions look simple, but when you build real systems like ERP, CRM, inventory management, banking, or e-commerce databases, these decisions affect performance, maintainability, scalability, and future upgrades.
This article explains the differences in a practical way using real examples, diagrams, and case-study-driven logic.
Problem Scenario
A logistics company is building a tracking system. The database has tables for:
Shipments
Customers
Tracking logs
Billing and invoices
Developers need:
A reusable query to list active shipments
Business logic for calculating shipment charges
A reusable system to fetch shipment reports based on filters such as status, date range, and carrier
Some developers write everything inside Stored Procedures, some write Functions to calculate charges, and others build complex Views that try to act like business logic engines. After a few months, the database becomes slow and hard to maintain.
This situation is common because developers misunderstand the purpose of Views, Functions, and Stored Procedures.
Understanding Each Component
1. SQL View
A View is a virtual table created from a query. It does not store physical data (unless materialized), but it simplifies reading complex queries.
Example
CREATE VIEW vw_ActiveShipments ASSELECT
s.ShipmentId,
s.TrackingNumber,
c.CustomerName,
s.Status,
s.CreatedDate
FROM Shipments s
INNER JOIN Customers c ON s.CustomerId = c.CustomerId
WHERE s.Status = 'Active';
Now instead of writing long JOIN queries, developers call:
SELECT * FROM vw_ActiveShipments;
When to Use a View
To simplify complex SELECT queries
To enforce read-only access to certain fields
To abstract underlying schema changes
For structured reporting queries
When Not to Use a View
For business logic calculations
When the goal is to update multiple tables
For loops, conditions, or procedural logic
Views are best for reusable read-only queries.
2. SQL Function
A Function returns a single value or a table. It is useful for reusable calculations or filtering logic.
Types:
Example: scalar function to calculate shipping tax:
CREATE FUNCTION fn_GetShippingTax (@Amount DECIMAL(10,2))
RETURNS DECIMAL(10,2)
ASBEGIN
RETURN @Amount * 0.18;
END;
Usage:
SELECT
ShipmentId,
TotalAmount,
dbo.fn_GetShippingTax(TotalAmount) AS TaxAmount
FROM Shipments;
Rules and Restrictions
| Feature | Function |
|---|
| Can return table/value? | Yes |
| Can modify data? | No |
| Can use TRY-CATCH? | Limited |
| Can call inside SELECT? | Yes |
| Can commit or rollback transactions? | No |
When to Use a Function
For reusable logic (tax, discount, age calculation)
When a value must be computed inside SELECT, WHERE, or JOIN
When returning filtered data as a Table-Valued Function
3. Stored Procedure
A Stored Procedure (SP) contains business logic, multiple SQL commands, and can perform read/write operations.
Example:
CREATE PROCEDURE sp_GetShipmentsByStatus
@Status NVARCHAR(50)
ASBEGIN
SELECT
ShipmentId,
TrackingNumber,
Status,
CreatedDate
FROM Shipments
WHERE Status = @Status;
END;
Usage:
EXEC sp_GetShipmentsByStatus 'Delivered';
When to Use Stored Procedures
For business logic
Logging, auditing, or modifying multiple tables
Returning multiple result sets
ETL, batch processing, or API integrations
Capabilities
| Feature | Stored Procedure |
|---|
| Can return multiple result sets? | Yes |
| Can handle transactions? | Yes |
| Can accept parameters? | Yes |
| Can use loops and conditions? | Yes |
| Can modify data? | Yes |
Real-World Workflow Diagram
┌─────────────────────┐
│ Application / API │
└───────────┬─────────┘
│
┌─────────▼─────────┐
│ Stored Procedure │ → Transaction, business logic
└─────────┬─────────┘
│
┌─────▼─────┐
│ Function │ → Calculations / rules
└─────┬─────┘
│
┌─────▼─────┐
│ View │ → Data abstraction layer
└────────────┘
Flowchart for Choosing the Correct Component
┌────────────────────────┐
│ Do you need to update │
│ or insert data? │
└───────────┬────────────┘
│ Yes
▼
Stored Procedure
│
└─────────────────────────────┐
│ No
▼
┌───────────────────────────────────────────┐
│ Do you need reusable calculation logic? │
└───────────────────┬───────────────────────┘
│ Yes
▼
Function
│
└───────────────────────┐
│ No
▼
Create a View
Summary of Differences
| Feature | View | Function | Stored Procedure |
|---|
| Main Purpose | Simplify SELECT | Reusable logic | Business logic |
| Data Modification | No | No | Yes |
| Can return table | Yes | Yes | Yes |
| Can use in SELECT | Yes | Yes | No |
| Supports Transactions | No | No | Yes |
Best Practices
Use Views as a read abstraction layer.
Use Functions for reusable computation and filtering logic.
Use Stored Procedures as the business logic layer.
Common Anti-Patterns to Avoid
| Anti-Pattern | Why It’s Bad |
|---|
| Writing business rules in Views | Impacts performance and maintenance |
| Using Scalar Functions inside SELECT on large tables | Causes Row-By-Row (RBAR) execution |
Using Stored Procedures to simulate Views with SELECT * | Hard to maintain and version control |
Case Study Result
In the logistics example, the refactoring resulted in:
Faster reporting (using Views)
Cleaner reusable calculations (Functions)
Better maintainable business logic (Stored Procedures)
Improved performance by 65 percent in shipment billing module
Final Conclusion
Views, Stored Procedures, and Functions solve different problems. When used correctly, they enforce a clean database architecture suitable for enterprise projects. When misused, they lead to performance bottlenecks and complex maintenance issues.