Run your rollback scripts.
If you don't have rollback scripts, then you're looking at restoring a copy of the database to a point before the deployment and then trying to synchronise data and structure changes. Not trivial, mistakes easy to make.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability