MySQL有两个不同的密码？

Question

I am sure they are passwords to different things but i am not sure what. When in terminal to connect to MySQL I enter /usr/LOCAL/mysql/BIN/mysql -h host -u username -p I am then prompted for a password and the password is ''. But when connecting to MySQL with PHP I use the following code and it works

DEFINE('DB_HOST', 'localhost'); 
DEFINE('DB_USER', 'root'); 
DEFINE('DB_PASS', 'root'); 

$dbc = mysqli_connect(DB_HOST, DB_USER, DB_PASS,) or 
die('could not connect: '. mysqli_connect_error() );

If i were to use DEFINE('DB_PASS', ''); it returns "Access denied for user 'root'@'localhost' (using password: NO)", why does there appear to be two separate passwords?

Answer 1

MySQL uses $user/$host/$password comparison by default, so your current setup has two different user accounts in MySQL - root and whatever username you supply on the command line. Each of those has its own password.

Also, if the account has no (ie empty) password you don't need to specify the -p flag on the CLI