How to determine the service pack of Sql Server
You can execute 

SELECT @@VERSION;


Which will give you the relevant information (note the bold, italicised SP1 from the example results)


  Microsoft SQL Server 2012 (SP1) - 11.0.3000.0 (X64)     Oct 19 2012
  13:38:57      Copyright (c) Microsoft Corporation     Developer Edition
  (64-bit) on Windows NT 6.2  (Build 9200: )