When querying data from MYSQL, using mysql_query() always returns false, but is there no problem with the SQL statement?

Question

<?php

//Create database connection

$conn=mysql_connect("localhost","arvin","123");

// Determine whether the data inventory connection is normal

if(!$conn)

{

die('Could not connect:'.mysql_error());

}

//Open the database

$selected=mysql_select_db("study",$conn);

//Write SQL statement

$sql1="select * from phone";

$result=mysql_query($sql1,$conn);

var_dump($result);

?>

Answer 1

I have never written a native database connection, but I feel that selecting a database is not used here