SQL User-Defined Functions: Syntax and Examples

Elevate your SQL skills with our guide to User-Defined Functions. Explore syntax and practical examples for efficient database development. Level up your SQL expertise now!

Kaibarta Sa

12/22/20233 min read

person holding black iPad
person holding black iPad


In programming, functions play a crucial role in organizing and reusing code. They allow us to break down complex tasks into smaller, manageable pieces, making our code more modular and easier to maintain. While most programming languages provide a set of built-in functions, they also allow us to define our own functions, known as user-defined functions. In this blog post, we will explore the concept of user-defined functions, their syntax, and provide examples to help you understand how to create and use them effectively.

What are User-Defined Functions?

User-defined functions, as the name suggests, are functions that are created by the user or programmer. These functions are designed to perform specific tasks or calculations based on the requirements of the program. By defining our own functions, we can encapsulate a set of instructions and give them a name, allowing us to reuse the code whenever needed.

Syntax of User-Defined Functions

To define a user-defined function, we follow a specific syntax. Let's break down the syntax into its individual components:

Function Declaration

The first step in creating a user-defined function is to declare it using the `function` keyword, followed by the name of the function. The function name should be meaningful and descriptive, reflecting the purpose of the function. It is good practice to use lowercase letters and underscores to separate words in the function name. Here's an example of a function declaration: function calculateSum() { // Function body } In the above example, we have declared a user-defined function named `calculateSum`.

Function Parameters

Functions can accept parameters, which are values that can be passed into the function for it to work with. Parameters are defined within parentheses after the function name. Multiple parameters can be separated by commas. Here's an example of a function declaration with parameters: function calculateSum(a, b) { // Function body } In the above example, the function `calculateSum` accepts two parameters, `a` and `b`.

Function Body

The function body contains the set of instructions or code that defines what the function should do. It is enclosed within curly braces `{}`. This is where you write the logic or calculations that the function will perform. Here's an example of a function with a body that calculates the sum of two numbers: function calculateSum(a, b) { let sum = a + b; return sum; } In the above example, the function calculates the sum of the parameters `a` and `b` and returns the result.

Function Return

The `return` statement is used to specify the value that the function should return after executing its instructions. It is optional and can be omitted if the function does not need to return any value. Here's an example of a function with a return statement: function calculateSum(a, b) { let sum = a + b; return sum; } In the above example, the function calculates the sum of the parameters `a` and `b` and returns the result using the `return` statement.

Calling a User-Defined Function

Once we have defined a user-defined function, we can call or invoke it within our code to execute its instructions. To call a function, we simply write its name followed by parentheses. If the function accepts parameters, we provide the values for those parameters within the parentheses. Here's an example of calling the `calculateSum` function: let result = calculateSum(5, 3); console.log(result); // Output: 8 In the above example, we call the `calculateSum` function with the values `5` and `3`. The function calculates the sum of these values and returns the result, which is then assigned to the variable `result`. Finally, we log the value of `result` to the console, which outputs `8`.

Benefits of User-Defined Functions

User-defined functions offer several benefits that contribute to writing clean and efficient code:

Code Reusability

By encapsulating a set of instructions within a function, we can reuse that code whenever needed. This reduces code duplication and makes our programs more modular and maintainable.


Functions allow us to abstract away the implementation details of a specific task. We can give a function a descriptive name that reflects its purpose, making our code more readable and easier to understand.


User-defined functions promote modularity by breaking down complex tasks into smaller, manageable pieces. Each function can focus on solving a specific subtask, making the overall code structure more organized and easier to debug.

Code Readability

By using user-defined functions, we can make our code more readable and easier to follow. Functions act as building blocks, allowing us to write code in a structured and logical manner.


User-defined functions are a powerful tool in programming that allows us to create reusable code blocks tailored to our specific needs. By understanding the syntax and examples provided in this blog post, you should now have a solid foundation for creating and using user-defined functions in your own programming projects. Remember, user-defined functions provide code reusability, abstraction, modularity, and improved code readability. Embrace the power of functions in your programming journey and unlock the potential for cleaner, more efficient code. Happy coding!