Top 10 Differences between Stored Procedure and Function in SQL Server

Last updated on August 7th, 2023 at 09:30 am

Stored procedures and functions are database objects which contain a set of SQL statements to execute a task. Both are different in many respects.

In this post, We will learn the differences between stored procedures and functions.

Before diving into the differences, it is important to understand the fundamental concepts such as stored procedures, functions, advantages, basic syntax, etc.

What is stored procedure?

In SQL Server, a Stored procedure is a collection of pre-compiled SQL statements saved in the database. It is like a reusable set of instructions or commands that can be called and executed over and over again.

The stored procedure accepts input and output parameters, performs DML operations or calculations, and may or may not return a value.

Now, why should we use stored procedures? Here are a few reasons:

• Reusability: Once you create a stored procedure, you can use it multiple times without having to rewrite the same code again and again. It saves you time and effort.
• Improved Performance: When you run a stored procedure for the first time, SQL Server creates a plan to execute it. This plan is saved and reused whenever you run the stored procedure again. As a result, the execution is faster because SQL Server doesn’t need to figure out how to run the commands every time.
• Security: Stored procedures can help protect your data. Instead of giving direct access to tables, you can control who can access the data by granting permissions to execute specific stored procedures. It adds a layer of security to your database.
• Efficiency: Stored procedures are pre-compiled, which means they are prepared and optimized before you even run them. It makes them faster than writing ad-hoc queries every time. It’s like having a well-organized kitchen where all the ingredients are easily accessible, saving you time and effort.
• Maintenance: If you need to change your database logic, you only need to update the stored procedure. You don’t have to modify every single part of your application that uses that logic. It makes it easier to maintain and update your code.

A stored procedure is a pre-compiled collection of SQL commands that we can reuse multiple times. It’s like having a ready-to-use script stored in the database.

To learn more about the stored procedure, please refer to the article Different types of Stored Procedures in SQL Server.

Syntax to create the stored procedure

CREATE PROCEDURE <procedure_name>
AS
BEGIN
	<sql_statements>
END

Syntax to execute the stored procedure

EXECUTE <procedure_name> <parameters seprated by comma>

What is function in SQL?

In SQL Server, a function is a reusable database object that encapsulates a set of SQL statements to perform specific tasks. Functions only accept input parameters, process data, and return a single value, such as a scalar value, table variable, or table result set.

They help to simplify complex queries, promote code modularity, and enhance code reusability within the database system.

Syntax to create a user-defined function (UDF)

CREATE FUNCTION <function_name> (<@paramater_name>   <datatype>)
RETURNS <return_datatype>
AS
BEGIN
 	<SQL statements>
    RETURN expression
END

Syntax to execute a user-defined function (UDF)

SELECT * FROM <Function_name>(Parameter)
-- OR
SELECT Field1,Field2 <function_name(parameters)> FROM table_name

Basic Difference Between Stored Procedure and Function in SQL Server

• Stored procedures are used to perform actions in the database, such as inserting or updating data. They can also retrieve data, but their main purpose is executing tasks. On the other hand, functions are used to calculate and return specific values based on input parameters from the database.
• A stored procedure can return zero or multiple values, and returning values is optional. On the other hand, a function is always bound to return a value and can only return a single value.
• In SQL Server, functions are limited to input parameters, while procedures can have both input and output parameters.
• In SQL, you can invoke functions from within stored procedures, but you cannot call procedures from functions.
• In SQL Server, stored procedures do not require a return type since they are not bound to return any value. Conversely, functions have a specified return type that indicates the data type of the value they will always return.
• The procedure allows SELECT and DML(INSERT/UPDATE/DELETE) statements, whereas Function allows only SELECT statements.

Function vs Stored Procedure in SQL

The following table describes the differences between functions and stored procedures in a SQL Server database.

Example: Stored Procedure

The following is an example of creating a Stored procedure in SQL Server to add two numbers.

-- Create a sample stored procedure
Create procedure AddNumbers(@num1 float, @num2 float)
as
begin
print 'The sum of '+cast(@num1 as varchar)+' + '+cast(@num2 as varchar)+' = '+ cast((@num1+ @num2) as varchar)
end
-- Execute stored procedure to print two numbers
Execute AddNumbers 20, 30;

Output:

If you execute the above code, you will be able to see the following result:

The sum of 20 + 30 = 50

Example: Function (UDF) in SQL Server

Let’s create a sample example of a Scalar Function (UDF)

-- Create a sample user defined function in SQL Server
Create function fn_AddNumbers(@num1 int,@num2 int)
returns int
as
Begin
    Return @num1 + @num2
End

-- Calling function in the SELECT statement
Select dbo.fn_AddNumbers(20,30) as result;
-- result: 50

FAQs

Summary

This blog provides detailed information about SQL Server stored procedures and functions. Now you understand the difference between stored procedures and functions and how to use them for your basic requirement.

• In SQL Server, A function must return a value, which is optional in a Stored Procedure.
• A Function can only have input parameters, whereas Procedures can have input and output parameters.
• You can call a function from a stored procedure, but you cannot call a procedure from a function in SQL Server.

Reference: tutorials point: function vs stored procedure

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• Having VS Where Clause in SQL
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• Stored Procedure in SQL Server – A Complete Guide [with Examples]
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Shekh Ali

Meet Sheikh Ali, a skilled Software engineer and passionate a blogger. He enjoys sharing his expertise in C#, Java, SQL, Design Patterns, and other related topics through his writing. When he's not coding, Sheikh Ali can often indulge in his passions for reading books and fitness training.

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