RULES
[ { UPDATE | UPSERT [ ALL ] } ]
[ { AUTOMATIC | SEQUENTIAL } ORDER ]
[ ITERATE (number) [ UNTIL (condition) ] ]
([ { UPDATE | UPSERT [ ALL ] } ]
 cell_assignment [ order_by_clause ] = expr
   [ [ { UPDATE | UPSERT [ ALL ] } ]
     cell_assignment [ order_by_clause ] = expr
   ]...
)