anchor.diff:  	| ( LPAREN table_references RPAREN )
   	| ( OJ table_reference LEFT OUTER JOIN table_reference ON expression )
   ;
  +
  +join_clause:
  +        (  (INNER | CROSS)? JOIN table_atom (join_condition)? )
  +    |
  +        (  STRAIGHT_JOIN table_atom (ON expression)?  )
  +    |
  +        (  (LEFT|RIGHT) (OUTER)? JOIN table_factor4 join_condition  )
  +    |
  +        (  NATURAL ( (LEFT|RIGHT) (OUTER)? )? JOIN table_atom )
  +    ;
   
   join_condition:
   	  (ON expression (expr_op expression)*) | (USING column_list)
  
positive.code: }
  
  @header {
  }
  
  stat:
  
negative.code: 	;
  
  table_references:
          table_reference ( (COMMA table_reference) | join_clause )*
  ;
  
  table_reference:
  