anchor.diff:     ;
   
   constdatetime
  -   : TIMESTAMP (OPEN_PAREN iconst CLOSE_PAREN)? opt_timezone
  -   | TIME (OPEN_PAREN iconst CLOSE_PAREN)? opt_timezone
  +   : (TIMESTAMP | TIME) (OPEN_PAREN iconst CLOSE_PAREN)? opt_timezone
      ;
   
   constinterval
  
positive.code:    ;
  
  plsql_opt_transaction_chain
     : AND (CHAIN | NO CHAIN)
     |
     ;
  
  
negative.code:    | RELATIVE_P a_expr
     | a_expr
     | ALL
     | (FORWARD | BACKWARD) (a_expr | ALL)?
     ;
     //https://www.postgresql.org/docs/current/plpgsql-cursors.html#PLPGSQL-CURSOR-OPENING
  
  