multi checkbox choice

Hi

I have form like this at attachment , the problem i want to choose two or more choise for each book
for example(book1--> economy and law)

type of books from database table ,and books at another table
i want to have these results

1---->law-Engineering
2---->law-Engineering-Economy

 

database tables structure

table(books)
book_num|book_name|book_type
---------------------------
1 |bookno1 |
2 |bookno2 |
3 |bookno3 |

table(booktype)


num|type_name
---------------------------
1 |Engineering
2 |law
3 |Economy

 
    <?
    $sql= "SELECT * ".
      "FROM books";
 
    $result=mysql_query($sql);?>
    <form name="myform" method="post" action="">
        <table>
        <tr>
        <td >no</td>
        <td >books</td>
    <?$sql= "SELECT * ".
      "FROM booktype"
      ;
    $result=mysql_query($sql);
    while($row=mysql_fetch_array($result))
    {?><td><? echo ' '.$row['type_name'].' '; }?></td>   
        </tr>
        <?
    while($row=mysql_fetch_array($result))
    {
 
 
    ?> <tr>
                <td><? echo $row[book_num]; ?></td>
        <td><? echo $row[book_name]; ?></td>
 
    <? $sqlt= "SELECT * ".
      "FROM booktype";
 
    $resultt=mysql_query($sqlt);
    while($rowt=mysql_fetch_array($resultt)){
    $tname=    $rowt[type_name];
  ?>
                   
    <td><input type="checkbox" name="typename[]" value=""></td><?}?>
                       
            </tr>
        <?} ?>
    <tr>
                       
                        </tr>
        </table><input type="submit" value="save" id="save" name="save"></form>

PHP:

I want to save the results in this way


book_num|book_name|book_type
---------------------------
1 |bookno1 |law,Economy
2 |bookno2 |Engineering
3 |bookno3 |law,Economy,Engineering