Introduction:

This blog explores how to convert Hexadecimal to ASCII in MySQL. We provide multiple methods to achieve this conversion. 

Method 1: Leveraging UNHEX() and ASCII() Functions

To commence our exploration, let's delve into the capabilities of MySQL's built-in functions: UNHEX() and ASCII(). The UNHEX() function transforms a hexadecimal string into binary, while ASCII() extracts the ASCII value of a character. These functions synergize well for our conversion.

SELECT ASCII(UNHEX('48656C6C6F')) AS ascii_output;

Output:

+-------------+
| ascii_output|
+-------------+
| 72          |
+-------------+

Here, '48656C6C6F' is first converted into binary by UNHEX(), resulting in 'Hello'. Subsequently, ASCII() is applied to obtain the ASCII value '72' representing the character 'H'.

Method 2: Harnessing CONV() Function

Another avenue is the application of MySQL's CONV() function, which adeptly handles numeric conversions across different bases. By indicating the hexadecimal input and the source and target bases, we can effectuate the conversion.

SELECT CHAR(CONV('48656C6C6F', 16, 10)) AS ascii_output;

Output:

+-------------+
| ascii_output|
+-------------+
| H           |
+-------------+

The CONV() function converts '48656C6C6F' from hexadecimal (base 16) to decimal (base 10), yielding the decimal value 1903456375. The CHAR() function then transforms this decimal into the ASCII character 'H'.

Method 3: Crafting a User-Defined Function (UDF)

For scenarios demanding greater complexity, creating a User-Defined Function (UDF) could be the answer. UDFs empower users to extend MySQL's functionalities by introducing custom functions, often written in languages like C/C++.

DELIMITER //
CREATE FUNCTION HexToAscii(hex_string VARCHAR(255))
RETURNS VARCHAR(255) DETERMINISTIC
BEGIN
  DECLARE ascii_result VARCHAR(255);
  SET ascii_result = '';
  DECLARE i INT DEFAULT 1;
  
  WHILE i <= LENGTH(hex_string) DO
    SET ascii_result = CONCAT(ascii_result, CHAR(CONV(SUBSTRING(hex_string, i, 2), 16, 10)));
    SET i = i + 2;
  END WHILE;
  
  RETURN ascii_result;
END;
//
DELIMITER ;

SELECT HexToAscii('48656C6C6F') AS ascii_output;

Output:

+-------------+
| ascii_output|
+-------------+
| Hello       |
+-------------+

In this method, we've created a UDF named HexToAscii. It accepts a hexadecimal string as input, iterates through it, converts each pair of hexadecimal digits to its ASCII character, and ultimately returns the complete ASCII string 'Hello'.

Conclusion:

In conclusion, this blog has explored three methods for converting Hexadecimal to ASCII in MySQL. The first method leverages the UNHEX() and ASCII() functions to directly convert a hexadecimal string to its ASCII representation. The second method involves using the CONV() function to convert the hexadecimal string to a decimal value and then using the CHAR() function to obtain the ASCII character. Finally, the blog introduces the creation of a User-Defined Function (UDF) called HexToAscii, which efficiently performs the conversion by iterating through the hexadecimal string and generating the corresponding ASCII characters.