anchor.diff:  	;
   */
   
  - table_ref: relation_expr opt_alias_clause # table_ref_simple
  -          | relation_expr opt_alias_clause tablesample_clause # table_ref_simple
  + table_ref:
  +           relation_expr opt_alias_clause tablesample_clause? # table_ref_simple
             | func_table func_alias_clause # table_ref_simple
  -          | LATERAL_P func_table func_alias_clause # table_ref_simple
             | xmltable opt_alias_clause # table_ref_simple
  -          | LATERAL_P xmltable opt_alias_clause # table_ref_simple
             | select_with_parens opt_alias_clause # table_ref_simple
  -          | LATERAL_P select_with_parens opt_alias_clause # table_ref_simple
  +          | LATERAL_P
  +                (
  +                    xmltable opt_alias_clause
  +                    |func_table func_alias_clause
  +                    |select_with_parens opt_alias_clause
  +                )# table_ref_simple
   //todo: joined_table was inlined to (partially) solve left-recursion problem;
   //          | joined_table
  -          | table_ref CROSS JOIN table_ref # table_ref_joined_tables
  -          | table_ref join_type JOIN table_ref join_qual # table_ref_joined_tables
  -          | table_ref JOIN table_ref join_qual # table_ref_joined_tables
  -          | table_ref NATURAL join_type JOIN table_ref # table_ref_joined_tables
  -          | table_ref NATURAL JOIN table_ref # table_ref_joined_tables
  -          | OPEN_PAREN table_ref CLOSE_PAREN opt_alias_clause  # table_ref_simple
  +
  +          | table_ref
  +                    (
  +                         CROSS              JOIN table_ref
  +                        |NATURAL join_type? JOIN table_ref
  +                        |        join_type? JOIN table_ref join_qual
  +                    )   # table_ref_joined_tables
  +
             | OPEN_PAREN
  -                (
  -                        //table_ref
  -                          table_ref CROSS JOIN table_ref
  -                        | table_ref join_type JOIN table_ref join_qual
  -                        | table_ref JOIN table_ref join_qual
  -                        | table_ref NATURAL join_type JOIN table_ref
  -                        | table_ref NATURAL JOIN table_ref
  -                )
  +                    table_ref
  +                    (
  +                         CROSS              JOIN table_ref
  +                        |NATURAL join_type? JOIN table_ref
  +                        |        join_type? JOIN table_ref join_qual
  +                    )?
             CLOSE_PAREN opt_alias_clause # table_ref_joined_tables
   ;
   
  
positive.code:                 |unicode_normal_form? NORMALIZED
              )
  
         | a_expr ISNULL
         | a_expr NOTNULL
         | row OVERLAPS row
  
         //NOT	right	logical negation
  
negative.code: 
  ;
  simple_select:
      /*??? unable to find in doc syntax like select  into sysrec * from system where name = new.sysname; - got from plpgsql.sql test script*/
  	  SELECT
  	        (
  	            opt_all_clause  into_clause  opt_target_list
  	            |distinct_clause target_list
  	        )
  	        into_clause from_clause where_clause group_clause  having_clause window_clause # simple_select_select
  	| values_clause # simple_select_values
  	| TABLE relation_expr # simple_select_table
  	/*this replacement solves mutual left-recursive problem betwee simple_select and select_clause */
  