SELECT查詢「大於」無法正常工作？

-1

我的代碼，這個功能寫在我的網站上顯示用戶消息：SELECT查詢「大於」無法正常工作？

function fetch_conversation_summery(){ 
    $sql = "SELECT 
       `conversations`.`conversation_id`, 
       `conversations`.`conversation_subject`, 
       MAX(`conversations_messages`.`message_date`) AS `conversation_last_reply` 
       MAX(`conversations_messages`.`message_date`) > `conversations_members`.`conversation_last_view` AS `conversation_unread` 
      FROM `conversations` 
      LEFT JOIN `conversations_messages` ON `conversations`.`conversation_id` = `conversations_messages`.`conversation_id` 
      INNER JOIN `conversations_members` ON `conversations`.`conversation_id` = `conversations_members`.`conversation_id` 
      WHERE `conversations_members`.`userid` = {$_SESSION['userid']} 
      AND `conversations_members`.`conversation_deleted` = 0 
      GROUP BY `conversations`.`conversation_id` 
      ORDER BY `conversation_last_reply` DESC"; 

    $result = mysql_query($sql); 

    $conversations = array(); 

    while (($row = mysql_fetch_assoc($result)) !== false){ 
     $conversations[] = array(
      'id'    => $row['conversation_id'], 
      'subject'   => $row['conversation_subject'], 
      'last_reply'  => $row['conversation_last_reply'], 
      'unread_messages' => ($row['conversation_unread'] == 1), 
     ); 
    } 

    return $conversations; 
}

雖然當我嘗試使用這個正確的頁面上，它會發出一個錯誤：

mysql_fetch_assoc() expects parameter 1 to be resource, boolean given in...

我所在問題是在查詢中，在該行：

MAX(`conversations_messages`.`message_date`) > `conversations_members`.`conversation_last_view` AS `conversation_unread`

雖然似乎有什麼我可以看到不對的地方，所有的表名是CORRE CT仍然是一個錯誤？有沒有人有任何想法可能造成這種情況？

P.S代碼工作正常，沒有我提到錯誤所在的MAX行。

來源

2014-04-07 user257234

什麼數據類型是你的'message_date'列？ –

message_date是一個10的INT。 – user257234

嘗試在運行查詢後添加'echo mysql_error（）;'。另外，你有沒有試圖用phpmyadmin（或其他應用程序）對數據庫運行查詢？ –

你缺少這行後一個逗號：

MAX(`conversations_messages`.`message_date`) AS `conversation_last_reply`

應該是：

MAX(`conversations_messages`.`message_date`) AS `conversation_last_reply`,

來源

2014-04-07 18:06:06 jeroen

嘗試更換此

MAX(`conversations_messages`.`message_date`) > `conversations_members`.`conversation_last_view` AS `conversation_unread`

通過

CASE WHEN MAX(`conversations_messages`.`message_date`) > `conversations_members`.`conversation_last_view` THEN max(`conversations_messages`.`message_date`) END AS `conversation_unread`

來源

2014-04-07 18:09:42

SELECT查詢「大於」無法正常工作？

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