anchor.diff:  ;
   
   table_factor1:
  -	table_factor2 (  (INNER | CROSS)? JOIN table_atom (join_condition)?  )?
  +	table_factor2 (  (INNER | CROSS)? JOIN table_atom (join_condition)? )?
   ;
   
   table_factor2:
  
positive.code: 	;
  
  table_references:
          table_reference ( COMMA table_reference )*
  ;
  
  table_reference:
  
negative.code: 
  subquery:
  	LPAREN select_clause RPAREN
  ;