sql dan script sederhana

<?php
/*
CREATE TABLE IF NOT EXISTS `soal` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `soal` text NOT NULL,
  `jawabA` text NOT NULL,
  `jawabB` text NOT NULL,
  `jawabC` text NOT NULL,
  `jawabD` text NOT NULL,
  `jawaban` tinyint(4) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='jawaban adalah posisi jawaban.. bila A maka 1' AUTO_INCREMENT=1 ;
*/

//-------------lakukan query
while($row=.......)
{
?><?=$row[soal];?><br>
A . <input type=checkbox value=1 name=jawab[<?=$row[id];?>] /><?=$row[jawabA]<br/>
B . <input type=checkbox value=2 name=jawab[<?=$row[id];?>] /><?=$row[jawabB]<br/>
C . <input type=checkbox value=3 name=jawab[<?=$row[id];?>] /><?=$row[jawabC]<br/>
D . <input type=checkbox value=4 name=jawab[<?=$row[id];?>] /><?=$row[jawabD]<br/>
<?php
}

/*
buat dapetin jawaban
*/
$nil=0;$nSoal=0;
foreach($_POST[jawab] as $id=>$val)
{
   $sql="select count(*) c from soal where id=$id and jawaban=$val";
  //bila nilainya 1 berarti benar
$nil+=$row[c];$nSoal++;

}

$nilai=100 * ($nil / $soal);
echo round($nilai);