asp.net and sql server

You need to use ajax requests to download data from your database. For example if you're having a TextBox (which will be an input field in HTML) then you can trigger a function to request for data according to the value in TextBox. 


For example, you can trigger ajax requests, like this...


$.ajax({
    url: 'server-side-page.aspx',
    data: $('#textBoxId').val()
    success: function (data) {
        // data contains the result from server,
        // append it to the tables or what ever
    }
});


You can at the very same time, have this code on the server side to fetch data from database.


@{
    // initialize and fetch data from database
    // and populate your web page, which would be
    // returned by the ajax request. 
}


This way you can download data for the Roll Number that is entered into TextBox. You can learn more about jQuery ajax here.

And what have you tried, or what is the schema for table. 


Sharing these information would help us to guide you any further.