How To Run A Function In SQL Server

As the founder of Enabla Technology, a leading IT Managed Services Provider in Australia, I’ve worked with hundreds of growing businesses that rely on efficient database solutions. Understanding how to run functions in SQL Server is not just a technical skill—it’s a business advantage. This comprehensive guide aims to simplify the concept of SQL Server functions, particularly user-defined functions, while helping your business boost performance, maintain modular programming practices, and stay secure.

Whether you’re enhancing Order Status reports, managing Network Traffic logs, or processing sales status in high-traffic environments, the ability to use scalar-valued functions and table-valued functions within SQL Server is a skill that saves time and adds long-term value. Let’s walk through everything you need to know.

Introduction

In the digital age, where responsive sites and interactive applications are standard expectations, SQL functions serve as a foundational skill for developers and IT administrators. They allow for modular programming by encapsulating logic into reusable blocks that can return a scalar value or a table. With schema-bound functions, you also ensure consistency and referential integrity across systems.

This blog covers built-in functions, user-defined functions, scalar-valued functions, and advanced topics like Common Language Runtime (CLR) functions, with real-life use cases and syntax examples using CREATE FUNCTION. Whether you’re learning in a classroom, a SQL community-led learning event, or self-paced with W3Schools Academy, this is your one-stop guide.

Types of Functions in SQL Server

Built-in Functions

SQL Server comes with a collection of code snippets packaged as built-in functions. These include:

• String operations
• Date/time processing
• Mathematical calculations
• System information retrieval

User-Defined Functions (UDFs)

UDFs are custom-built and offer powerful features like control, reusability, and simplified debugging. There are three major types:

• Scalar-valued functions – Return a single scalar value like a number or string.
• Inline table-valued functions – Return a table based on a single SELECT query.
• Multi-statement table-valued functions – Use multiple SQL statements and return a table.

You can execute these with the CREATE FUNCTION statement, often found in online code editor environments or built into enterprise development workflows.

Understanding SQL Server Functions

What Are SQL Functions?

Functions are a modular way to perform repeated tasks. They help reduce human error, allow for faster execution, and enforce consistency. Functions are deterministic and can be written to handle tasks like converting HSL colors, performing currency calculations, or managing term trends within educational institutions or online content platforms.

Key Differences: Functions vs Stored Procedures

Feature	Function	Stored Procedure
Must Return Value	Yes	Optional
Database Side Effects	No	Yes
Can Be Used in Queries	Yes	No
Error Handling Support	Minimal	Full
Modular & Testable	High	Moderate

Built-in SQL Server Functions

Built-in functions are quick tools for streamlining database logic. You’ll find them used across internet users’ interactions—from web analytics to typing speed tests.

Function Types & Use Cases

Function	Category	Use Case
LEN	String	String length detection
GETDATE	Date & Time	Insert current timestamp
ROUND	Math	Round decimals, e.g., pricing calculations
ISNULL	Logical	Handle null values
CURRENT_USER	System Info	User tracking across responsive websites

Explore these in any online code editor or integrated SQL IDE.

User-Defined Functions: The Power Tool

UDFs give you flexibility. Imagine processing pine cones in a forestry application—each has size, type, and location data. A scalar-valued function could extract just the pine cone type from a massive dataset.

Benefits of UDFs

• Modular programming with isolated logic
• Faster execution when reused properly
• Supports schema binding and parallel query processing
• Ideal for use in educational institutions and enterprise software alike

Creating a User-Defined Function

CREATE FUNCTION dbo.CalculateGST(@amount DECIMAL(10,2))
RETURNS DECIMAL(10,2)
AS
BEGIN
    RETURN @amount * 0.10;
END;

Running SQL Server Functions

Scalar-Valued Function Example

SELECT dbo.CalculateGST(1000);

Table-Valued Function Example

SELECT * FROM dbo.GetMonthlySales('2025-07');

In WHERE Clause Example

SELECT * FROM Orders WHERE dbo.CheckOrderStatus(order_id) = 'Pending';

Practical Scenarios: Built-In vs User-Defined

Scenario	Recommended Function Type
Convert color formats (e.g., HSL)	User-defined scalar function
Display current date	Built-in GETDATE()
Filter network usage above threshold	Table-valued function
Rank typing speed from log table	Multi-statement table function
Custom pricing logic	Scalar-valued function

Managing and Maintaining Functions

• ALTER FUNCTION: Modify existing logic
• DROP FUNCTION: Remove outdated code
• Permissions: Use GRANT EXECUTE & REVOKE for controlled access
• View Definitions: Query sys.objects and sys.sql_modules
• Report Error: Use structured exception handling within TRY…CATCH

Performance Optimization Tips

• Avoid nested UDFs in complex queries
• Use indexes on columns referenced inside UDFs
• Leverage local cursors for row-by-row logic (with caution)
• Analyze execution plans using SQL Server Management Studio

Advanced Concepts

Common Language Runtime (CLR) Integration

Leverage the .NET framework to write complex logic that exceeds T-SQL’s native limitations.

User-Defined Aggregates

Create custom aggregation logic for advanced reports, such as combining sales status across multiple regions.

Responsive Website Integration

Use UDFs to feed into backend systems that support responsive website templates or choice questions in online assessments.

Collection of Code Snippets for Learning

Maintain a private collection of code snippets with labeled use cases—ideal for onboarding new team members or offering exclusive content to clients.

Security & Compliance

• Limit UDF access to only required users
• Use EXECUTE AS to ensure correct execution context
• Document every function’s purpose for audit compliance
• Encourage W3Schools Academy or similar Learning Experience platforms for staff training

FAQs

Q1: What’s the difference between scalar and table-valued functions?
A scalar function returns a single value. Table-valued functions return an entire table—inline or multi-statement.

Q2: Can I test functions in an online code editor?
Yes, many support SQL syntax and allow quick prototyping before deployment.

Q3: How do I track performance for frequently used UDFs?
Enable query statistics, monitor execution times, and look into sys.dm_exec_query_stats.

Q4: Do schema-bound functions run faster?
Yes, they improve performance by limiting schema changes during runtime.

Q5: Are there resources for continued learning?
Explore W3Schools Academy, SQL Server documentation, and community-led events.

Conclusion

Mastering functions in SQL Server transforms your ability to build secure, high-performing systems. From scalar-valued functions used in Order Status reports to advanced CLR logic for data science tasks, these tools empower businesses to move faster and with more precision.

At Enabla Technology, we help Australian businesses with 20–120 staff take advantage of the latest database strategies, cloud platforms, and security best practices. Want access to exclusive content, engaging video tutorials, or hands-on help with SQL, reporting, and performance optimization?

Contact us today and elevate your Learning Experience.