MySQL从一个表插入到另一个表

Question

I am trying to select a random address from one table and add it at one of the columns on the other table but it keeps saying "no database selected"

if ($_SESSION[address] == "")
{
    $db = @mysql_select_db($db_bitcoins,$connection)
        or die(mysql_error());
    $sql = "SELECT Count(*) FROM address";
    $result = @mysql_query($sql, $connection) or die(mysql_error());
    $rnum = mysql_num_rows($result);
    $rrr=rand(1,rnum);
    $sql = "SELECT * FROM address WHERE id = '$rrr'";
    $result = @mysql_query($sql, $connection) or die(mysql_error());
    while ($sql = mysql_fetch_object($result)) {
        $_SESSION[address]  = $sql -> ads;
        $db = @mysql_select_db($db_name,$connection)
                        or die(mysql_error());
        $sql = "UPDATE $table_name SET bitaddress = $_SESSION[address] WHERE username = '$user' and password = password('$pass')";
        $result = @mysql_query($sql, $connection) or die(mysql_error());
    }
}

Thanks in advance!

Answer 1

检查是否正确指定了数据库名称（SID），端口和主机IP，并且数据库是否可以访问（如果不在PC中）。

Answer 2

EDIT:I found out $db_bitcoins wasn't set, thanks for the help everyone! I get another exception now "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1" this time