PHP的：如何使用准备好的语句从SQL数据库中获取最新的日期时间？

Question

In the following code i am trying to fetch only the newest datetime from a sql table full of email adresses (which are all the same) and datetimes, using a prepared statement:

 $sql = "SELECT * FROM usertokens WHERE user_mail = ?;";
      //Create a prepared statement
      $stmt = mysqli_stmt_init($conn);
      //prepare prepared statement
      if (!mysqli_stmt_prepare($stmt, $sql)) {
        echo "SQL failed";
      } else {
        //Bind parameters to the placeholder
        mysqli_stmt_bind_param($stmt, "s", $email);
        //run params
        mysqli_stmt_execute($stmt);
        $result = mysqli_stmt_get_result($stmt);
        $resultCheck = mysqli_num_rows($result);
        if ($row = mysqli_fetch_assoc($result)) {       
            $dt = date_create_from_format('Y-m-d H:i:s', $row['user_date']);
             }}

At the moment it fetches only the first entry. How can i select the newest date time(and i do not want to select the lowest entry)? The table would look like this:

:---user_mail---------user_date---------
:-----------------------------------------------
:---some@mail.com----2018-06-06 20:28:16
:---some@mail.com----2018-06-06 20:31:24
:---some@mail.com----2018-06-06 20:33:44

Answer 1

您可以使用ORDER BY和LIMIT完成此目标：

$sql = "SELECT * FROM usertokens WHERE user_mail = ? ORDER BY user_date DESC LIMIT 1;";