Используйте как
// mysqli_connect(host,username,password,dbname,port,socket);
$con = mysqli_connect("localhost", "root", "", "your_db");
// mysqli_select_db(connection, dbname);
$db = mysqli_select_db($con, "dbname");
$q = "select*from tablename";
// mysqli_query(connection,query,resultmode);
$qry = mysqli_query($con, $q);
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