我怎样才能得到结果?:
$check = mysql_query("select username, email, case
when max(username = '$username') > 0 and max(email = '$email') > 0 then 'both'
when max(username = '$username') > 0 then 'username'
when max(email = '$email') > 0 then 'email'
end
from school_users
WHERE username = '$username' or email = '$email'") or die(mysql_error());
当它存在时,我需要“用户名”或“电子邮件”或“两者”。我如何接收这些变量?