AES_DECRYPT function with Mysql

[g_grillo]

Hy guys,
I tried to put the AES_DECRYPT function into a WHERE statement doing the following:
SELECT * FROM tb_user WHERE pwd = AES_DECRYPT(AES_ENCRYPT("stringPWD","key"),"key");

but MySql always returns an empty set ...key and pwd are correct. Does anybody know the right way to do it?
Thanks :-)

[g_grillo]

sorry guys,
I forgot the first rule : keep it simple! the only necessary function is the AES_DECRYPT() one, so the corret way to do what I need is:
select * from tb_user where pwd = AES_DECRYPT("stringPWD", "key");
this one work fine :-)