Data with all the best combination

For fun, the recursive subquery approach ported to XQuery :

select *
from xmltable(
     'declare function local:iterator ($run as xs:integer, $expr as xs:string, $list as xs:integer*) as element(r)*
      {
        for $n at $i in $list
        let $r := $run + $n
        let $e := if ($expr) then concat($expr, " + ", $n) else string($n)
        return if ($r <= 1100) 
               then ( if ($r >= 900) then <r><s>{$r}</s><e>{$e}</e></r>  else () )
                  | local:iterator($r, $e, subsequence($list, $i + 1))
               else ()
      }; (: 
      local:iterator(0, "", /ROW/NUMBER)'
passing sys_xmlgen(sys.odcinumberlist(671,238,598,438,244,153,504,480,19,352,326,444))
columns expr varchar2(4000) path 'e'
      , s    number         path 's'
) 
order by s ;

Hi,

As I was thinking about this problem - if I were to code it in C, I would write it as a recursive function. For a set of one number, if it is in the desired range select it, if not don't. For a set of two or more numbers, order descending (this makes the function more efficient). Call the function twice: once for the same range, with the remaining numbers (this will give the solutions that do NOT include the largest number); and once more with the remaining numbers and the range limits decreased by the first number (to get the solutions that DO include the first number). It is for this second part of the recursive call that I would start with the largest number - this makes the remaining problem smaller.

I don't know if this can be done in SQL (although I assume it can be done in PL/SQL). Perhaps a recursive subquery can be rigged to do this. Heck, I don't even know if this is in fact your solution, or equivalent to it! I'll keep this thought for later, when I will know more.

Cheers,    mathguy-ro