This can be done two ways without any code.
As a database type form
Design a Form, Select Database as the type, go through the wizard to connect to your SQL table
However if you are very advanced, multiple databases, multiple unrelated tables, write to multiple tables then you will run into the limitations of this type of form.
or with Web Services
This gives you the ability to do about whetever you need to and with the Database Accelerator Web Services Suite Qdabra Database Accelerator Suite Version 2.1.2808 - Developer
You do not even need to know how to make one or exactly how they work! You set them up as data connections and then use the information they can provide.
Included is an Active Directory service that will get the form user's name and department to write into your table ( and make sure no one else is putting him on Leave). It also includes granular permissions so that you can make sure only he and HR can see he is on Leave. And then we have sample forms with work flow and routing already included so that he can route the request for approval or additional sign off and approval.
Let me know if you need more informaiton or would like a demo.