Difference Between Procedure and Function in SQL
SQL is one of the world's most widely used database management systems. It is used to manage and manipulate data in a variety of ways, using a range of different tools and techniques. Two of the most commonly used SQL features are functions and procedures. But what exactly are they, and how do they differ?
In this blog post, we'll explore the key differences between SQL functions and procedures and help you determine which one is right for your data management needs.
Table of Contents
- Difference Between Procedure and Function in SQL
- What is the Function in SQL
- What is the Procedure in SQL
- Key Differences and Similarities Between Procedures and Functions in SQL
What is the Difference Between Procedure and Function in SQL?
| Parameter |
SQL Function |
SQL Procedure |
| Definition |
A SQL function is a pre-written, reusable code block to perform a specific task. It is created and stored in the database and can be called from an SQL statement or another function. | A SQL procedure is a pre-written, reusable code block designed to perform a specific task or set of tasks. It is created and stored in the database and can be called from an SQL statement or another procedure. |
| Syntax |
Defined using the CREATE FUNCTION statement |
Defined using the CREATE PROCEDURE statement |
| Execution |
It can be executed from within a SELECT statement or another function |
Must be explicitly called using the EXECUTE statement or another procedure |
| Return Value |
Always returns a single value |
May or may not return a value |
| Purpose |
Used to perform a single calculation or operation |
Used to perform a series of actions |
| Input Parameter |
Can accept input parameters |
Can accept input parameters |
| Output Parameter |
Cannot have output parameters |
Can have output parameters |
| Examples |
SUM, CONCAT, YEAR |
Stored Procedures, Triggers, User-Defined Functions |
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What are the Functions in SQL?
A SQL function is a pre-written, reusable code block to perform a specific task. It is created and stored in the database and can be called from an SQL statement or another function.
They are mainly used to perform calculations, manipulate data, and retrieve information from the database. They can take one or more input parameters and return a single value.
Types of SQL Function
SQL offers a range of functions to perform different types of tasks. Some of the most commonly used SQL functions are:
- Mathematical Functions: These functions are used to perform mathematical operations on numeric data.
- Examples include SUM, AVG, MAX, MIN, and COUNT.
- String Functions: These functions are used to manipulate string data.
- Examples include LEFT, RIGHT, CONCAT, and LENGTH.
- Date and Time Functions: These functions are used to manipulate dates and times.
- Examples include NOW, DATE, TIME, and YEAR.
- Conversion Functions: These functions are used to convert data from one data type to another.
- Examples include CAST, CONVERT, and PARSE.
- Aggregate Functions: These functions are used to perform calculations on groups of data.
- Examples include GROUP BY, HAVING, and ROLLUP.
Let's have some examples to get a better understanding of functions in SQL.
Examples of SQL Function
- SUM: This function calculates the sum of a set of numeric values.
- For example, the following SQL statement calculates the sum of the "sales" column in the "orders" table:
SELECT SUM(sales) FROM orders;
- CONCAT: This function combines two or more strings into a single string.
- For example, the following SQL statement combines the "first_name" and "last_name" columns in the "employees" table:
SELECT CONCAT(first_name, ' ', last_name) AS full_name FROM employees;
- YEAR: This function extracts the year from a date value.
- For example, the following SQL statement retrieves the year from the "hire_date" column in the "employees" table:
SELECT YEAR(hire_date) AS hire_year FROM employees;
What are the Procedures in SQL?
A SQL procedure is a pre-written, reusable code block designed to perform a specific task or set of tasks. It is created and stored in the database and can be called from an SQL statement or another procedure. They are mainly used to perform complex data manipulations, enforce data integrity rules, or automate repetitive tasks. They can take one or more input parameters and return values or output parameters.
Types of Procedures in SQL
- Stored Procedures: These are procedures that are stored in the database and can be called from an SQL statement or another procedure.
- They can be used to perform complex data manipulations, enforce data integrity rules, or automate repetitive tasks.
- Triggers: These procedures are automatically executed in response to a specific event or condition.
- They can be used to enforce data integrity rules, log database changes, or update related tables.
- User-Defined Functions: These are procedures that are created by users to perform specific tasks that are not available in the built-in SQL functions.
- They can be used to perform complex data manipulations or to format data in a specific way.
Let's have some examples to get a better understanding of procedures in SQL.
Example of Procedure in SQLL
- Stored Procedure: This procedure updates the "orders" table with a new order:
CREATE PROCEDURE add_order( IN order_id INT, IN customer_id INT, IN order_date DATE, IN order_total DECIMAL(10,2) ) BEGIN INSERT INTO orders VALUES (order_id, customer_id, order_date, order_total); END;
- Trigger: This trigger logs changes to the "employees" table:
CREATE TRIGGER emp_update AFTER UPDATE ON employees FOR EACH ROW BEGIN INSERT INTO emp_log (emp_id, update_date) VALUES (NEW.emp_id, NOW()); END;
- User-Defined Function: This function calculates the age of a person based on their date of birth:
CREATE FUNCTION calc_age(dob DATE) RETURNS INT BEGIN RETURN YEAR(CURDATE()) - YEAR(dob) - (DATE_FORMAT(CURDATE(), '%m%d') < DATE_FORMAT(dob, '%m%d')); END;
When to Choose - SQL Function vs SQL Procedure
Important factors to remember while choosing between the SQL Function and Procedure.
- Complexity of the Task: If you need to perform a complex set of calculations or operations on a dataset, a function might be the best tool for the job.
- Functions are designed to perform a single calculation or operation and can simplify complex calculations.
- Repetitive Tasks: A procedure might be more appropriate if you need to perform a series of repetitive tasks on a dataset.
- Procedures can be used to automate repetitive tasks, such as updating a set of records or generating a report.
- Data Manipulation: A procedure might be more appropriate if you need to perform complex data manipulations, such as joining tables or filtering data.
- Procedures can perform a series of actions on a dataset and can be used to enforce data integrity rules.
- Input and Output Parameters: A procedure might be more appropriate if you need to pass input or output parameters to the code block.
- While functions can accept input parameters, they cannot have output parameters.
Best Practices for Using SQL Functions and Procedures
- Keep your code simple and easy to understand.
- Use descriptive names for your functions and procedures.
- Test your code thoroughly before deploying it to a production environment.
- Use comments to explain what your code is doing and why.
- Avoid using global variables in your code.
- Use error handling to prevent unexpected errors from occurring.
Conclusion
In this article, we have briefly discussed the difference between procedure and function in SQL with the help of different examples. Hope you will like the article.
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Vikram has a Postgraduate degree in Applied Mathematics, with a keen interest in Data Science and Machine Learning. He has experience of 2+ years in content creation in Mathematics, Statistics, Data Science, and Mac... Read Full Bio
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