Question

For onchange of the Dropdown list fetch the data from the db with out submitting the form.

I need to check the data according to the selected data of Dropdown list with database(example: select count(*) from employee).

That is, Consider Dropdown List has 3 options.
if User selects 2nd option then, function(method) should be called to get the data from the database.
if the Query returns 10 the i need to show some message. but the form should not submity here, until he clicks the submit button.

Answer 1

You can use JavaScript here to post data to server and return response.
For example you can use jQuery .alax() method when the onchange event of your dropdown is fired.

$('#select').change(function(){
  $.ajax({
    url: 'http://domain.name/somescript.php',
    data: {item: $this.find('option:selected').val()}
    success: function(xhr){
      // analyze recieved data from server
      if(xhr.responseText == '10')
        alert('some message');
    }    
  });
});