SQL Server Stored Procedure vs Function

Understanding the difference between stored procedure and function is important for developers and admins when working with SQL Server. Both are important for creating reusable SQL code, but they have different purposes and characteristics.

The stored procedure doesn’t have parameters and no need to return any results, whereas the function will return values.

We will discuss some main differences between SQL server stored procedure and functions.

Table of Contents

Stored Procedure Vs Function in SQL Server

Now, we will see some key differences between a function and a stored procedure in an SQL server.

Stored Procedure in SQL Server

A stored procedure is an SQL statement stored together in the database. Based on the parameters we pass, it will perform DML operations on the database
When we create a stored procedure in SQL Server, the SQL Server compiles the procedure and creates an execution plan for it. The execution plan is used to execute the method.
A stored procedure is a pre-compiled object and will be valid till we make some changes.
Stored Procedures have the advantage of being executed on the server and performing tasks before returning the results to the client.
A stored procedure can accept inputs using input parameters and return the output using output parameters.

Syntax for Stored Procedure

The general syntax of creating a stored procedure in SQL Server.

CREATE PROCEDURE Procedure name
AS

BEGIN
  sql_statements
END

Example of Stored Procedure

CREATE PROCEDURE SQL
AS
BEGIN
  PRINT 'Welcome to SQL WORLD'
END

Next, we have to use the EXEC statement to execute a procedure. The query to execute the procedure is given below.

EXEC SQL
GO

Function in SQL Server

A function is also a database object in SQL Server. It is a sequence of SQL statements that take only input parameters, execute tasks, and return the output.
A function in SQL Server is compiled and executed whenever it is called. Additionally, a function can only return a single value or table.

Syntax for Function

Here is the general syntax of creating a function in SQL Server.

CREATE FUNCTION [schema_name.] function_name()
RETURNS return_data_type
AS 
BEGIN
  sql_statement
END

Example of Function

CREATE FUNCTION dbo.simplefunction()
RETURNS varchar(20)
AS 
BEGIN
  RETURN 'Welcome to sql world'
END

Now, we have to call a function for that, we have to use the SELECT statement. The query to call the function is given below.

 
SELECT dbo.simplefunction() AS 'Message'
GO

After executing the above example, we will get the below output.

Stored Procedure Vs Function in SQL Server

Significant Differences Between Stored Procedure and Function

Look at the tabular below for the major difference between stored procedure and function in SQL Server.

Stored Procedure	Functions
A stored procedure returns single or multiple values.	Function will return single values only if it is mandatory.
We can use DML queries such as insert, update, select, etc… with procedures.	We cannot use a function with Data Manipulation queries. Only Select queries are allowed in functions.
Both input and output will be supported	Only inputs are permitted
Try Catch blocks are used to handle the exception	Catch block can be used to handle exception
A stored procedure can be called a function	A function cannot called a stored procedure
In JOIN clauses, the stored procedure will not be used.	In JOIN clauses, function will be used.
Create Procedure <Procedure name> As Begin End	Create Function <Function name> Returns <Datatype> As Begin Return End

Stored Procedure Vs Function Performance in SQL

Both stored procedure and function are database objects in SQL Server. Many developers often get confused about when to create which object to create. So, in this section, we will discuss the performance difference between a procedure and a function.

A query executed within a function and one executed within a procedure have almost the same speed. So, query execution speed is not a significant factor in terms of performance.

The main factor that affects the performance of a procedure or function is the situation in which it is used. So, here are some points to consider while using a function or method.

A function can only use the SELECT statement. We cannot use other DML or DDL statements within a function. For this purpose, we can use a stored procedure. Stored procedures support using all types of DML, DDL, and SELECT statements.
On the other hand, we cannot use a stored procedure in SELECT or DML statements. Instead, we can use an SQL Server function, which is easily used in these statements.
A function in an SQL server can only return a single value or table, but what if we can return multiple values? We can use a stored procedure to return multiple values as output in such a case.

Advantages of Stored Procedure in SQL

Storage procedures are used for programming within modules. Stored procedures are created once, saved, and called whenever needed. It allows for faster execution. It reduces network traffic and improves data security as well.
Because the script is only kept in one place, maintaining the method on the server is much easier than maintaining copies on numerous client PCs.
Stored procedures can be created with any Java-integrated development environment (IDE). They can then be implemented at any network architectural level.
The reason stored procedures increase scalability is that they divide server-side application operations.

Advantages of Function in SQL

By using the function, we can reduce the program time. This is important for microcomputers with limited storage.
The function is used in different programs. C programmers do not need to start from scratch.
The function will be helpful to for code modularity. Every code block is split into independent units that have distinct functions.

Conclusion

Both stored procedures and functions are database objects that contain a set of SQL statements to perform a task. However, they are different from each other in many ways. I hope this tutorial on Stored procedure vs. Function was helpful!

Both stored procedures and functions are database objects in SQL Server. Still, these objects are different in numerous ways.