DES_DECRYPT has been deprecated from MariaDB 10.10.0, and will be removed in a
future release.

Syntax
------

DES_DECRYPT(crypt_str[,key_str])

Description
-----------

Decrypts a string encrypted with DES_ENCRYPT(). If an error occurs, this
function returns NULL.

This function works only if MariaDB has been configured with TLS support.

If no key_str argument is given, DES_DECRYPT() examines the first byte of the
encrypted string to determine the DES key number that was used to encrypt the
original string, and then reads the key from the DES key file to decrypt the
message. For this to work, the user must have the SUPER privilege. The key
file can be specified with the --des-key-file server option.

If you pass this function a key_str argument, that string is used as the key
for decrypting the message.

If the crypt_str argument does not appear to be an encrypted string, MariaDB
returns the given crypt_str.

URL: https://mariadb.com/kb/en/des_decrypt/