---
title: "How to create a user-defined function (UDF) in SQL, and what are its benefits?"  
description: "How to create a user-defined function (UDF) in SQL, and what are its benefits?"  
author: "Sandra Emily"  
published: 2023-09-04  
updated: 2023-09-26  
canonical: https://www.mindstick.com/forum/159816/how-to-create-a-user-defined-function-udf-in-sql-and-what-are-its-benefits  
category: "mssql server"  
tags: ["sql server", "sql"]  
reading_time: 2 minutes  

---

# How to create a user-defined function (UDF) in SQL, and what are its benefits?

How to create a user-defined [function](https://www.mindstick.com/articles/13001/multi-statement-table-valued-user-defined-function-in-sql-server) ([UDF](https://www.mindstick.com/blog/420/difference-between-store-procedure-and-udf-user-define-function)) in [SQL](https://www.mindstick.com/articles/13115/types-of-keys-in-sql-or-oracle-database), and what are its [benefits](https://www.mindstick.com/articles/75377/surprising-benefits-of-learning-to-code)?

## Replies

### Reply by Aryan Kumar

To create a user-defined function (UDF) in SQL, you use the `CREATE FUNCTION` statement. The syntax for the `CREATE FUNCTION` statement is as follows:

SQL

```plaintext
CREATE FUNCTION function_name (parameter1, parameter2, ...) RETURNS return_type AS
{
  function body
}
```

- `function_name` is the name of the function.
- `parameter1`, `parameter2`, and so on are the parameters that the function takes. The parameters can be any valid SQL data type.
- `return_type` is the data type that the function returns.
- `function body` is the code that the function executes.

For example, the following SQL code creates a user-defined function called `add()` that takes two integer parameters and returns the sum of the two integers:

SQL

```plaintext
CREATE FUNCTION add (a INT, b INT) RETURNS INT AS
{
  RETURN a + b;
}
```

Once the function has been created, it can be used in SQL statements just like any other built-in function. For example, the following SQL statement uses the `add()` function to calculate the sum of two columns:

SQL

```plaintext
SELECT add(column1, column2) FROM table;
```

User-defined functions have a number of benefits, including:

- **Code reuse:** User-defined functions allow you to reuse code. Once you have created a function, you can use it in any SQL statement where you need to perform the same operation.
- **Modularity:** User-defined functions make your code more modular and easier to maintain. You can group related code into functions, which makes it easier to understand and modify your code.
- **Performance:** User-defined functions can improve the performance of your SQL statements. This is because the database engine can cache the compiled execution plan for a function, which can reduce the amount of time it takes to execute the function.
- **Encapsulation:** User-defined functions can encapsulate complex logic, which can make your code more readable and easier to understand.

Overall, user-defined functions are a powerful tool that can make your SQL code more reusable, modular, performant, and readable.


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Original Source: https://www.mindstick.com/forum/159816/how-to-create-a-user-defined-function-udf-in-sql-and-what-are-its-benefits

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