anchor.diff:      | ext_type=id '(' scale=DECIMAL ')'
       | ext_type=id IDENTITY ('(' seed=DECIMAL ',' inc=DECIMAL ')')?
       | double_prec=DOUBLE PRECISION?
  -    | unscaled_type=id 
  +    | unscaled_type=id
       ;
   
   default_value
  
positive.code: 
  create_xml_index
      : CREATE PRIMARY? XML INDEX id ON table_name '(' id ')'
      (USING XML INDEX id (FOR (VALUE | PATH | PROPERTY)?)?)? 
      index_options?
      ';'?
      ;
      
  // https://msdn.microsoft.com/en-us/library/ms187926(v=sql.120).aspx
  create_or_alter_procedure
      : ((CREATE (OR ALTER)?) | ALTER) proc=(PROC | PROCEDURE) procName=func_proc_name_schema (';' DECIMAL)?
  
negative.code: time_zone
      : AT_KEYWORD TIME ZONE expression
      ;
  
  primitive_expression
      : DEFAULT | NULL_ | LOCAL_ID | constant
      ;
  