php - INSERT unless exist in other table -

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i have users table on wesite , want write function take email column , insert diffrent table, mailing_list, if email isn't exist in there.

for question can assume each table have columns: id,username, email.

this current code:

$get_mails = $db->query("select `username`,`email`,`email_approved`,`ver` `users` ver='yes' && email_approved='1'"); while ($mails = $get_mails->fetch_assoc())  {     if ($db->query("select `email` `mailing_list` email='".$mails['email']."'")->num_rows == 0)  {         $db->query("insert `mailing_list` values('','".$mails['email']."','".$mails['username']."')");              } }

as can see it's not efficient. there way in insert query itself?

thank you.

one (kinda dirty) solution put unique index on email field in mailing list, prevent double entries won't have select query first.

edit, example:

$db->query (     "insert ignore `mailing_list`      select '',email,username `users`     ver = 'yes' , email_approved = '1'" );

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