UDATE查詢與PHP和MySQL

Question

嵌套CASE語句我有測驗例如嵌套的SQL查詢來更新多個表。它包含兩個case語句，該語句在對數據庫執行查詢時檢查特定條件。下面是代碼：

// form data 
$edit_qid = isset($_POST['editqid']); 
$edit_question = isset($_POST['editquestion']); 
$edit_ans1 = isset($_POST['editanswer1']); 
$edit_ans2 = isset($_POST['editanswer2']); 
$edit_ans3 = isset($_POST['editanswer3']); 
$edit_correct = isset($_POST['editcorrect']); 

// answer ids (comes from another query and it's valid) 
while ($rows = mysqli_fetch_assoc($result_aid)) { 
    $aid[] = $rows['aid']; 
} 

// update of chosen question and answer options to DB 
$upd_question = "UPDATE `question_bank` qtbl INNER JOIN `answer_bank` atbl 
         SET qtbl.`question`='".$edit_question."', 
          atbl.`answer`= CASE WHEN atbl.`aid`='".$aid[0]."' THEN '".$edit_ans1."' 
               WHEN atbl.`aid`='".$aid[1]."' THEN '".$edit_ans2."' 
               WHEN atbl.`aid`='".$aid[2]."' THEN '".$edit_ans3."' 
              END 
          atbl.`correct` = CASE WHEN ".$edit_correct."=='1' THEN '1' 
                WHEN ".$edit_correct."=='2' THEN '1' 
                WHEN ".$edit_correct."=='3' THEN '1' 
                ELSE '0' 
              END 
        WHERE qtbl.`qid`=atbl.`question_id` AND qtbl.`qid`='".$edit_qid."'"; 
mysqli_query($mysqli, $upd_question) or die ("<b>Update of question failed:</b> " . mysqli_error($mysqli)); 

可變$edit_correct包含任一值1，2或3相對於回答字符串和根據上述查詢到DB那裏將被保存的1或0（真/假），這意味着該如果值是1，那麼真正的將被保存爲第1個答案選項等這段代碼的

跑步給了我以下錯誤：

Update of question failed: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'atbl.`correct` = CASE WHEN 2=='1' THEN '1' WHEN 2=='2' THEN '1' ' at line 7 

任何想法來解決這個問題？提前致謝。

UPDATE

而且，我有以下條件檢查：

,atbl.`correct` = CASE WHEN '". if($edit_correct=='1') {echo 1;} ."' THEN '1' 
         WHEN '". if($edit_correct=='2') {echo 1;} ."' THEN '1' 
         WHEN '". if($edit_correct=='3') {echo 1;} ."' THEN '1' 
         ELSE '0' 
       END 

，並得到這個錯誤：Parse error: syntax error, unexpected 'if' (T_IF)

Answer 1

你必須把逗號介乎兩列，試試這個代碼：

$upd_question = "UPDATE `question_bank` qtbl INNER JOIN `answer_bank` atbl 
         SET qtbl.`question`='".$edit_question."', 
          atbl.`answer`= CASE WHEN atbl.`aid`='".$aid[0]."' THEN '".$edit_ans1."' 
               WHEN atbl.`aid`='".$aid[1]."' THEN '".$edit_ans2."' 
               WHEN atbl.`aid`='".$aid[2]."' THEN '".$edit_ans3."' 
              END 
          ,atbl.`correct` = CASE WHEN ".$edit_correct."=='1' THEN '1' 
                WHEN ".$edit_correct."=='2' THEN '1' 
                WHEN ".$edit_correct."=='3' THEN '1' 
                ELSE '0' 
              END 
        WHERE qtbl.`qid`=atbl.`question_id` AND qtbl.`qid`='".$edit_qid."'"; 
mysqli_query($mysqli, $upd_question) or die ("<b>Update of question failed:</b> " . mysqli_error($mysqli)); 

在第二種情況下你可以使用IF（）語句，使用IF會得到更多可讀的代碼。