anchor.diff:      : USE database=id ';'?
       ;
   setuser_statement
  -    : SETUSER user=STRING
  +    : SETUSER user=STRING?
       ;
   
   dbcc_clause
  
positive.code:     ;
  
  batch
      : sql_clauses go_statement*
      ;
  
  sql_clauses
  
negative.code: 
  // https://msdn.microsoft.com/en-us/library/ms188332.aspx
  execute_statement
      : EXECUTE execute_body
      ;
  
  execute_body
      : (return_status=LOCAL_ID '=')? (func_proc_name | expression) (execute_statement_arg (',' execute_statement_arg)*)? ';'?
      | '(' execute_var_string ('+' execute_var_string)* ')' (AS? (LOGIN | USER) '=' STRING)? ';'?
      ;
  
  execute_statement_arg
  