Where 條件

1. Where 條件運算子：
   

   = != > < >= <=
   

2. 查詢 dyw_author='dywang' 的紀錄。
   

   [root@kvm8 html]# mysql -uroot -p123qwe \
   -e "use dyw; select * from dyw_tbl where dyw_author='dywang';"
   +--------+-----------+------------+-----------------+
   | dyw_id | dyw_title | dyw_author | submission_date |
   +--------+-----------+------------+-----------------+
   |      3 | MySQL     | dywang     | 2014-12-12      |
   +--------+-----------+------------+-----------------+
   

3. 可用 AND 及 OR 結合多個條件。
   

   [root@kvm8 ~]# mysql -uroot -p123qwe \
   -e "use dyw; select * from dyw_tbl where dyw_author='dywang' OR dyw_id=1;"
   +--------+-----------+------------+-----------------+
   | dyw_id | dyw_title | dyw_author | submission_date |
   +--------+-----------+------------+-----------------+
   |      1 | PHP       | david      | 2014-12-24      |
   |      3 | MySQL     | dywang     | 2014-12-12      |
   +--------+-----------+------------+-----------------+
   

4. 原 php 程式的查詢變數 $sql 加入 where 條件。

   [root@kvm8 html]# vim selectrecord.php 
   [root@kvm8 html]# cat selectrecord.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
           WHERE dywphp_author="dywang"';
   
   mysql_select_db('dywphp');
   $retval = mysql_query( $sql, $conn );
   if(! $retval )
   {
     die('Could not get data: ' . mysql_error());
   }
   while($row = mysql_fetch_array($retval, MYSQL_ASSOC))
   {
       echo "Dywphp ID :{$row['dywphp_id']}  <br> ".
            "Title: {$row['dywphp_title']} <br> ".
            "Author: {$row['dywphp_author']} <br> ".
            "Submission Date : {$row['submission_date']} <br> ".
            "--------------------------------<br>";
   } 
   mysql_free_result($retval);
   echo "Fetched data successfully\n";
   mysql_close($conn);
   ?>
   

5. 開啟瀏覽器，連上網址 http://kvm8.deyu.wang/selectrecord.php，網頁上列出資料表 dywphp_tbl 中的紀錄，其中第一筆紀錄時間為 0000-00-00 ，因為在網頁以函數 NOW() 輸入時間，php 程式將其判斷為字串。