MySQL Functions: String, Numeric, Stored, and User-Defined Functions Great 2025

What Are MySQL Functions?

MySQL functions are built-in or user-defined operations that allow you to manipulate data efficiently. These functions process input values and return results, helping developers format, compute, and analyze data within MySQL queries.

There are four main categories of MySQL functions:

• String Functions – Manipulate text values
• Numeric Functions – Perform calculations
• Stored Functions – Custom functions stored in the database
• User-Defined Functions (UDFs) – External functions created with programming languages like C or C++

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Why Use MySQL Functions?

Using MySQL functions provides several benefits, such as:
✅ Enhanced Data Processing – Perform computations directly within MySQL instead of relying on external scripts.
✅ Improved Performance – Reduce network traffic by processing data within the database.
✅ Better Data Consistency – Ensure uniform data formatting across multiple applications.

For example, suppose users want dates displayed as DD-MM-YYYY instead of YYYY-MM-DD. Instead of modifying the application logic, we can use MySQL’s DATE_FORMAT() function to achieve this efficiently.

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Types of MySQL Functions

1. String Functions in MySQL

MySQL string functions allow manipulation of text-based data.

Example: Convert Text to Uppercase

sql

SELECT `movie_id`, `title`, UCASE(`title`) AS `upper_case_title`

FROM `movies`;

✅ This query converts movie titles to uppercase.

Common MySQL String Functions:

Function	Description	Example Query	Output
UCASE()	Converts text to uppercase	SELECT UCASE(‘hello’);	HELLO
LCASE()	Converts text to lowercase	SELECT LCASE(‘HELLO’);	hello
CONCAT()	Joins multiple strings	SELECT CONCAT(‘My’, ‘SQL’);	MySQL
LENGTH()	Returns string length	SELECT LENGTH(‘MySQL’);	5
TRIM()	Removes spaces from text	SELECT TRIM(‘ SQL ‘);	SQL

2. Numeric Functions in MySQL

Numeric functions allow calculations on numerical data.

Example: Perform Arithmetic Operations

sql

SELECT 23 + 6 AS addition, 23 – 6 AS subtraction, 23 * 6 AS multiplication, 23 / 6 AS division;

✅ Performs basic arithmetic operations on numbers.

Common MySQL Numeric Functions:

Function	Description	Example Query	Output
ROUND()	Rounds numbers to the nearest whole number	SELECT ROUND(23 / 6);	4
FLOOR()	Rounds down to the nearest integer	SELECT FLOOR(23 / 6);	3
CEIL()	Rounds up to the nearest integer	SELECT CEIL(23 / 6);	4
MOD()	Returns remainder of division	SELECT 23 MOD 6;	5
RAND()	Generates a random number	SELECT RAND();	0.8345

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3. Stored Functions in MySQL

Stored functions are custom functions created within MySQL.

Example: Creating a Stored Function

sql

DELIMITER |

CREATE FUNCTION check_due_date(return_date DATE)

RETURNS VARCHAR(3)

DETERMINISTIC

BEGIN

    DECLARE result VARCHAR(3);

    IF CURDATE() > return_date THEN

        SET result = ‘Yes’;

    ELSE

        SET result = ‘No’;

    END IF;

    RETURN result;

END |

DELIMITER ;

✅ This function checks if a rented movie is overdue.

Using the Stored Function in a Query

sql

SELECT `movie_id`, `return_date`, check_due_date(`return_date`) AS overdue FROM `movierentals`;

✅ Returns whether a movie is overdue.

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4. User-Defined Functions (UDFs) in MySQL

User-defined functions extend MySQL capabilities using programming languages like C or C++.

Steps to Create a UDF in MySQL

1. Write the function in C/C++.
2. Compile it as a shared library (.so or .dll).

Register the function in MySQL using:
sql
CREATE FUNCTION function_name RETURNS INTEGER SONAME ‘library_file.so’;

4. Use the function in queries like built-in functions.

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MySQL Functions vs. Stored Procedures

Feature	Functions	Stored Procedures
Returns a value	✅ Yes	❌ No
Accepts parameters	✅ Yes	✅ Yes
Used in SQL queries	✅ Yes	❌ No
Supports complex logic	❌ No	✅ Yes

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Key Takeaways

✔ MySQL functions enhance database performance by processing data efficiently.
✔ String functions manipulate text, while numeric functions handle calculations.
✔ Stored functions allow reusability within MySQL, while user-defined functions extend MySQL’s capabilities.
✔ Using built-in MySQL functions reduces application workload and improves consistency.

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Ready to Optimize Your MySQL Queries?

Start using MySQL functions today to improve efficiency and streamline database operations!

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