Populate dropdown list from database when dropdownlist selectindex changed SharePoint 2010

I have dorpdown1 and dropdown2 in my SharePoint list. When item is selected from the dropdown1, it should retrieve data from database and populate the dropdown2 based on dropdown1 parameter.

Which one is the best practice?

Jquery, client object model, custom code? Please provide related links if you have any.

In our environment they won’t allow manual changes.  it should be deployable script or code.

Appreciate your help.

Surya.

Surya.P