无法使PDO SQL查询正常工作

Question

I can't get this query to work. It only shows the first DB entry. Any ideas greatly appreciated.

/* prepare */

$sql = "SELECT personal.firstName, personal.lastName, etc. 
        FROM personal 
        LEFT JOIN exam 
        ON personal.P_ID=exam.P_ID 
        LEFT JOIN contact 
        ON exam.P_ID=contact.P_ID 
        WHERE exam.Level = ? 
        AND exam.Centre!='' ORDER BY exam.Centre";

$stmt = $db->prepare($sql);

/* Execute */ $stmt->execute(array($level));

/* Fetch */
            $row = $stmt->fetch(PDO::FETCH_ASSOC);    





/*  Display  */
                    echo '<table>
                         <tr>
                    <td>Name</td>
                    <td>Surname</td>
                    <td>Paid?</td>
                    <td>Etc</td>
                    <td>Etc</td>
                    <td>Etc</td>
                        </tr>';

if ($row) { foreach ($row as $key => $value)

              {
                echo '<td>';
                echo $value;
                echo '</td>';
            }
               echo '</tr>';
          }
       echo '</table>';

Answer 1

A simple tutorial for you to get it right.

1. Take your mysql query that works

     $sql = "SELECT * FROM t WHERE a = $a AND b = '$b'"; 

2. Make sure it works. If not - make it work first.

3. Take out every variable you interpolate in it ( along with all corresponding formatting, including slashes and quotes ), and put a question mark in place of them.

     $sql = "SELECT * FROM t WHERE a = ? AND b = ?"; 

4. Move these variables into execute() in the form of array

     $sql = "SELECT * FROM t WHERE a = ? AND b = ?"; $stm = $db->prepare($sql); $stm->execute(array($a,$b)); 

5. Everything works.

6. If still not - configure your PDO and PHP in order to see errors if any , read the error message and take appropriate action.

To get your data in the proper format you have to use proper fetch method

     $data = $stm->fetchAll();
     foreach ($data as $row) {
       echo $row['id'];
       // do whatever
     }

Please refer to tag wiki for other methods

Answer 2

I'm new at PDO as well, but from your code I noticed that there is no :centre in the query there, so that parameter won't bind?

Another thing is in WHERE exam.Level:level , are you sure you meant this and not: WHERE exam.Level = :level ?