刪除內連接行

Question

我創建了兩個表，簡單註釋和評論者，並將它們連接到INNER JOIN。

• Simplecomments是每個評論者的每一個細節，涉及其評論，reg_date，commentorid等...
• 評論者是評論者的個人信息有下列：ID，姓名，電子郵件..

我已經加入他們成功，但我很難從聯合表中刪除。

我想使它像這樣的邏輯：

1. 如果有一個名爲--let評註的最後一行說A--然後同時刪除他/她的評論詳細信息和他/她自己從桌子上。

2. 否則如果A已評論很多次，有不同的意見，刪除了他/她的意見的細節，但讓他/她的個人信息仍然因爲A有沒有其他意見。

這是我如何做了它：

if (!empty($_POST["delete"])) 
{ 
    foreach ($_POST["delete"] as $key => $value) 
    { 
     $resultid = $conn->query("SELECT commentorid FROM `simplecomments` WHERE id=".$value); 
     $rowid = $resultid->fetch_assoc(); 

     $outputdelete = $rowid["name"] . " has been deleted" . "<br>"; 

     $deletedname = $deletedname.$outputdelete; 
     $RES = mysql_num_rows($resultid); 
     $counter = 0; 
      while($row = $RES) 
      { 
       //IF IT'S LAST ROW, DELETE COMMENTOR AND HIS/HER COMMENTDETAILS 
       if(++$counter == $results) { 
        $resultid = $conn->query("DELETE FROM `commentor`"); 
       } 
       //ELSE JUST DELETE HIS/HER COMMENTDETAILS, LET HIS/HER INFO REMAIN 
       else{ 
        $resultid = $conn->query("DELETE FROM `simplecomments` WHERE id=".$value); 
       } 
      } 
    } 

} 

但是代碼將無法正常工作。我得到一個錯誤：

Warning: mysql_num_rows() expects parameter 1 to be resource [..]...

Answer 1

考慮運行DELETE...INNER JOIN和DELETE與子查詢條件語句，避免PHP查詢獲取循環與if/else的邏輯似乎是以下幾點：

1. 刪除任何評註者的個人資料，如果評論他/她只有一條評論
2. 如果他/她有多個（即多個）評論，則只刪除評論者的評論。

是的，所有三個DELETE可以在所有ID上同時運行，因爲互斥條件放在前兩個和最後一個之間。因此，前兩個影響行或最後一個影響每次迭代的行。未受影響的人將從兩個表中刪除零行。

此外，simplecomments記錄首先刪除，因爲這個表可能與評註外鍵約束，因爲它一個一對多的關係。最後，下面假設評論 ID傳遞到循環（不是評論或 id）。

PHP（使用參數，假定$ conn是一個mysqli的連接對象）

foreach ($_POST["delete"] as $key => $value) { 

    // DELETE COMMENTS AND THEN PROFILE FOR COMMENTORS WITH ONE POST  
    $sql = "DELETE FROM `simplecomments` s 
      WHERE s.id = ? 
      AND (SELECT COUNT(*) FROM `simplecomments` sub 
        WHERE sub.commentorid = s.commentorid) = 1"; 
    $stmt = $conn->prepare($sql); 
    $stmt->bind_param("i", $value); 
    $stmt->execute(); 
    $stmt->close(); 

    $sql = "DELETE c.* FROM `simplecomments` c 
      INNER JOIN `simplecomments` s ON s.commentorid = c.id 
      WHERE s.id = ? 
      AND (SELECT COUNT(*) FROM `simplecomments` sub 
        WHERE sub.commentorid = s.commentorid) = 1"; 
    $stmt = $conn->prepare($sql); 
    $stmt->bind_param("i", $value); 
    $stmt->execute(); 
    $stmt->close(); 


    // DELETE COMMENTS FOR COMMENTORS WITH MULTIPLE POSTS BUT KEEP PROFILE 
    $sql = "DELETE FROM `simplecomments` s 
      WHERE s.id = ? 
      AND (SELECT COUNT(*) FROM `simplecomments` sub 
        WHERE sub.commentorid = s.commentorid) > 1";  
    $stmt = $conn->prepare($sql); 
    $stmt->bind_param("i", $value); 
    $stmt->execute(); 
    $stmt->close(); 
} 

或者，對於DRY-ER方法中，循環的SQL語句中的陣列：

$sqls = array(
      0 => "DELETE FROM `simplecomments` s WHERE s.id = ? AND (SELECT COUNT(*) FROM `simplecomments` sub WHERE sub.commentorid = s.commentorid) = 1", 
      1 => "DELETE c.* FROM `simplecomments` c INNER JOIN `simplecomments` s ON s.commentorid = c.id WHERE s.id = ? AND (SELECT COUNT(*) FROM `simplecomments` sub WHERE sub.commentorid = s.commentorid) = 1", 
      2 => "DELETE FROM `simplecomments` s WHERE s.id = ? AND (SELECT COUNT(*) FROM `simplecomments` sub WHERE sub.commentorid = s.commentorid) > 1" 
     ); 

foreach ($_POST["delete"] as $key => $value) { 
    foreach($sqls as $sql) { 
     $stmt = $conn->prepare($sql); 
     $stmt->bind_param("i", $value); 
     $stmt->execute(); 
     $stmt->close(); 
    } 
}