Can you suggest me for Any Script or snippets of dopdown value given to database using jquery and ajax in php file.
dopdown value given to database
What does that mean? You sure you don't have it the other way around? Do you mean pull values from a database and populate a dropdown menu?
Means pull value directly fetch by database.
It's no different from how you would a pull data from the database in a normal $_POST php file. All you do is use $.ajax instead.
If you're just getting data and not changing it on the server, use $.get (or $.ajax with GET) or even $.getJSON - depending on how you get your info from the server. Do not use $.post (or $.ajax with POST) unless you're making changes on the server, e.g. insert, delete or update (or changes to a file etc).