doudaotui4297 2017-04-10 08:14
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SQL中的LIKE不起作用

I'm using a PDO to run this query, is there a way to see if the query return false? and why my query return nothing when I expect a result?

                $selectsql = "SELECT `firstname`,`surname`,`phone`,`address`,`username`,`StudentID` FROM `student_info` WHERE ? LIKE ?";
                $selectstmt = $conn->prepare($selectsql);
                $selectstmt->execute(array($searchby,"%{$searchval}%"));
                while($data = $selectstmt->fetch(PDO::FETCH_ASSOC)){
                  echo "
                  <tr>
                    <td>{$data['firstname']}</td>
                    <td>{$data['surname']}</td>
                    <td>{$data['phone']}</td>
                    <td>{$data['address']}</td>
                    <td>{$data['username']}</td>
                    <td>Delete Account</td>                    
                  </tr>
                  ";
                  var_dump($data);
                }   

I var dumpped the $searchby and the $searchval and they seems fine to me, no mistype or whatsoever.

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  • douhui9631 2017-04-10 10:05
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    The problem with your query is here :

    $selectsql = "SELECT firstname`,`surname`,`phone`,`address`,`username`,`StudentID` FROM `student_info` WHERE ? LIKE ?";
    

    That placeholder after where is messing up your query, after the where clause there should be a column name, by the way I see $searchby changes based on the item selected by the user. One thing you should note is that :

    Table and Column names cannot be replaced by parameters in PDO.

    Your query should look like.

    <?php
    
    $search = "%".$searchval."%";
    $selectsql = "SELECT `firstname`,`surname`,`phone`,`address`,`username`,`StudentID` FROM `student_info` WHERE $searchby LIKE ?";
        $selectstmt = $conn->prepare($selectsql);
        $selectstmt->execute([$search]);
        $results = $selectstmt->fetch((PDO::FETCH_ASSOC));
    
        if(count($results) > 0){
          var_dump($results);
            foreach($results as $data):?>
              <tr>
                  <td><?php echo $data['firstname'];?></td>
                  <td><?php echo $data['surname'];?></td>
                  <td><?php echo $data['phone'];?></td>
                  <td><?php echo $data['address'];?></td>
                  <td><?php echo $data['username'];?></td>
                  <td>Delete Account</td>                    
            </tr>
    
          <?php
              endforeach;
        }else{
    
          echo "no results found";
        }
    ?>
    
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
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