Syntax:
AES_DECRYPT(crypt_str,key_str[,init_vector])

This function decrypts data using the official AES (Advanced Encryption
Standard) algorithm. For more information, see the description of
AES_ENCRYPT().

The optional initialization vector argument, init_vector, is available
as of MySQL 5.6.17. As of that version, statements that use
AES_DECRYPT() are unsafe for statement-based replication and cannot be
stored in the query cache.

URL: http://dev.mysql.com/doc/refman/5.6/en/encryption-functions.html

