Deploying to an existing database from VS 2010 on TFS
For SSDT, when you choose Publish to generate a script the advanced options include "Always re-create database". Untick that and you're good to go.



Same option applies if you do a local debug build.



Similar options buried in the old VS2010 Database Project options somewhere.

To be honest, from the description of what you're doing SSDT and/or VS2010 database projects are overkill. Scribble a script in SSMS and be done with it.