PHP 和 MySQL - 處理 NULL 示例

你可以根據 NULL 值使用 if...else 條件來準備查詢。

以下示例從外部獲取 tutorial_count ，然後將它與表中可用的值進行比較。

示例

將以下示例複製並貼上為 mysql_example.php −

<html>
   <head>
      <title>Handling NULL</title>
   </head>
   <body>
      <?php
         $dbhost = 'localhost';
         $dbuser = 'root';
         $dbpass = 'root@123';
         $dbname = 'TUTORIALS';
         $mysqli = new mysqli($dbhost, $dbuser, $dbpass, $dbname);
         $tutorial_count = null;
         if($mysqli->connect_errno ) {
            printf("Connect failed: %s<br />", $mysqli->connect_error);
            exit();
         }
         printf('Connected successfully.<br />');
   
         if( isset($tutorial_count )) {
            $sql = 'SELECT tutorial_author, tutorial_count
               FROM  tcount_tbl
               WHERE tutorial_count = ' + $tutorial_count;
         } else {
            $sql = 'SELECT tutorial_author, tutorial_count
               FROM  tcount_tbl
               WHERE tutorial_count IS NULL';
         }
         $result = $mysqli->query($sql);
           
         if ($result->num_rows > 0) {
            while($row = $result->fetch_assoc()) {
               printf("Author: %s, Count: %d <br />",
                  $row["tutorial_author"], 
                  $row["tutorial_count"]);               
            }
         } else {
            printf('No record found.<br />');
         }
         $mysqli->close();
      ?>
   </body>
</html>

輸出

訪問部署在 apache Web 伺服器上的 mysql_example.php 並驗證輸出。

Connected successfully.
No record found.

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