使用大约50000条记录更新表的所有行上的特定字段

Question

i have a table that holds my users information like username , password , name , family , etc. already when a user register in my site her password hashes with one md5() function then insert into table. my table have about 50000 records now. but now i want to hash their passwords with two md5() function again for security issues. for that i write below code that first selects all of the users and then execute a update Query for change passwords:

$allMembers =   mysql_query("select `username`,`password` from `members`",$conn);


if (mysql_num_rows($allMembers) > 0){

    while($row  =   mysql_fetch_array($allMembers)){

            $oldPass    =   $row['password'];

            $newPass    =   md5(md5('Hello'.$oldPass.'Friends'));

            mysql_query("update `members` set `password`='$newPass' where `username`='".$row['username']."'",$conn);
    }
}

echo("Yes");

but when i run this code It took very little and produce No Data Received message . but now how i update the password field in my large table ?

Edit :i was used salt + md5 but removed it in my code for Summarization :)

Answer 1

Just run it as a single query:

UPDATE `members` SET `password`=MD5(MD5(`password`))

BTW double MD5 is useless. you can MD5 + salt or SHA1 + salt if you want better security.