[Programie]

I think you have to write variables without quotes.
I mean that:

Код:

samp_mysql_connect("MYSQL_HOST","MYSQL_USER","MYSQL_PASS");
samp_mysql_select_db("MYSQL_DB");

Try that:

Код:

samp_mysql_connect(MYSQL_HOST,MYSQL_USER,MYSQL_PASS);
samp_mysql_select_db(MYSQL_DB);

Or you have to append .dll to the plugin name in your server.cfg:
plugins mysql.dll


But I'm not shure.