Sorting 排序

1. 排序的語法 ORDER BY 經常與 WHERE ... LIKE 條件一起使用。可以使用任何一個欄位排序，也可以多個欄位一起排序，排序結果可以「升序」或「降序」排列。
   

   [root@kvm8 ~]# mysql -uroot -p123qwe \
   -e "use dyw; select * from dyw_tbl order by dyw_id asc;"
   +--------+-----------+------------+-----------------+
   | dyw_id | dyw_title | dyw_author | submission_date |
   +--------+-----------+------------+-----------------+
   |      1 | c++       | peter      | 2014-12-24      |
   |      3 | MySQL     | dywang     | 2014-12-12      |
   +--------+-----------+------------+-----------------+
   [root@kvm8 ~]# mysql -uroot -p123qwe \
   -e "use dyw; select * from dyw_tbl order by dyw_id desc;"
   +--------+-----------+------------+-----------------+
   | dyw_id | dyw_title | dyw_author | submission_date |
   +--------+-----------+------------+-----------------+
   |      3 | MySQL     | dywang     | 2014-12-12      |
   |      1 | c++       | peter      | 2014-12-24      |
   +--------+-----------+------------+-----------------+
   

2. php 程式的查詢變數 $sql 加入 ORDER BY dywphp_author DESC 條件。

   [root@kvm8 ~]# cd /var/www/html/
   [root@kvm8 html]# vim sorting.php
   [root@kvm8 html]# cat sorting.php
   <?php
   $dbhost = 'localhost:3306';
   $dbuser = 'root';
   $dbpass = '123qwe';
   $conn = mysql_connect($dbhost, $dbuser, $dbpass);
   if(! $conn )
   {
     die('Could not connect: ' . mysql_error());
   }
   $sql = 'SELECT dywphp_id, dywphp_title, 
                  dywphp_author, submission_date
           FROM dywphp_tbl
           ORDER BY  dywphp_author DESC';
   
   mysql_select_db('dywphp');
   $retval = mysql_query( $sql, $conn );
   if(! $retval )
   {
     die('Could not get data: ' . mysql_error());
   }
   while($row = mysql_fetch_array($retval, MYSQL_ASSOC))
   {
       echo "Tutorial ID :{$row['dywphp_id']}  <br> ".
            "Title: {$row['dywphp_title']} <br> ".
            "Author: {$row['dywphp_author']} <br> ".
            "Submission Date : {$row['submission_date']} <br> ".
            "--------------------------------<br>";
   } 
   echo "Fetched data successfully\n";
   mysql_close($conn);
   ?>
   

3. 開啟瀏覽器，連上網址 http://kvm8.deyu.wang/sorting.php，出現兩筆紀錄且以 ID 降序排列。