anchor.diff:  
   // https://msdn.microsoft.com/en-us/library/ms176118.aspx
   drop_index
  -    : DROP INDEX (IF EXISTS)? name=id ';'?
  +    : DROP INDEX (IF EXISTS)? name=id (ON table_name)? ';'?
       ;
   
   // https://msdn.microsoft.com/en-us/library/ms174969.aspx
  
positive.code: STDEVP:                                S T D E V P;
  SUM:                                   S U M;
  TAKE:                                  T A K E;
  THROW:                                 T H R O W;
  TIES:                                  T I E S;
  TIME:                                  T I M E;
  
negative.code: // https://msdn.microsoft.com/en-us/library/ms188066.aspx
  table_constraint
      : (CONSTRAINT id)?
         ((PRIMARY KEY | UNIQUE) clustered? '(' column_name_list (ASC | DESC)? ')' index_options? (ON id)?
         | CHECK (NOT FOR REPLICATION)? '(' search_condition ')')
      ;
  
  