如果单元格为空，则不会从数据库中获取电子邮件

Question

I write a code to fetch emails of all users and then save them in a txt file but some users don't have and email because they registered using phone number so when i am trying to fetch
it dump in txt file like http://prntscr.com/5wf7cv

I want if cell is empty/NULL don't fetch anything Anyone can help me to Fix it?

    $sql=mysql_query("SELECT * FROM user  "); 
    while($row = mysql_fetch_array($sql)) {

 $email = $row['email']   ;

  $fp = fopen("emaillist.txt", "a");
$savestring = "
$email";
fwrite($fp, $savestring);
fclose($fp);
}
echo  "DONE ";

Answer 1

Change the query to

SELECT * FROM user  WHERE email != NULL