Código HTML:
<!-- form.html -->
<form method="post" action="result.php">
<select name="tabla">
<option value="electronica">electronica</option>
<option value="computacion">computacion</option>
</select>
</form> Código PHP:
<?php
// result.php
extract($_POST);
$sql="SELECT * FROM $tabla";
.
.
.
?>