Subtotal less than or equal to a max value

Question

Hi,
I have the following values in a table:
drop table t;
create table t (key number, ind varchar2(1), num number);
insert into t (key,ind,num) values (1,'Y',2);
insert into t (key,ind,num) values (2,'Y',10);
insert into t (key,ind,num) values (3,'Y',12);
insert into t (key,ind,num) values (4,'Y',9);
insert into t (key,ind,num) values (5,'Y',1);
insert into t (key,ind,num) values (6,'Y',1);
insert into t (key,ind,num) values (7,'Y',8);
insert into t (key,ind,num) values (8,'Y',1);
insert into t (key,ind,num) values (9,'N',11);
insert into t (key,ind,num) values (10,'N',6);
commit;The values are:
test@ORA92> select * from t order by key;
       KEY I        NUM
         1 Y          2
         2 Y         10
         3 Y         12
         4 Y          9
         5 Y          1
         6 Y          1
         7 Y          8
         8 Y          1
         9 N         11
        10 N          6
10 rows selected.
test@ORA92>For all rows with ind = "Y", I want to add "num" as long as the subtotal is less than or equal to a max value (15). For all rows with ind = "N", I want the sum of "num".
It should be as follows:
       KEY I        NUM
         1 Y          2    <- consider this, as subtotal is now 2 which is < 15
         2 Y         10   <- consider this, as subtotal is now 12 which is < 15
         3 Y         12   <- ignore this, as subtotal would be 24 which is > 15; keep running total as 12.
         4 Y          9   <- ignore this, as running total would be (12+9=) 21, which is > 15; keep running total as 12
         5 Y          1   <- consider this, as running total is now (12+1=) 13, which is <= 15
         6 Y          1   <- consider this, as running total is now (13+1=) 14 which is <= 15
         7 Y          8   <- ignore this, as running total would be (14+8=) 22, which is > 15; keep running total as 14
         8 Y          1   <- consider this, as running total is now (14+1=) 15, which is <= 15
         9 N         11 <- add this to subtotal for ind = "N"; subtotal = 11
        10 N          6 <- add this to subtotal for ind = "N"; subtotal = (11+6=) 17
Return "ac" (subtotal for ind = "Y") = 15 - the one we got at key = 8
Return "dc" (subtotal for ind = "N") = 17 - the one we got at key = 10I have a pl/sql block that does the same:
test@ORA92>
test@ORA92> --
test@ORA92> -- To derive "ac" value:
test@ORA92> --   Loop through t, and for ind = "Y", keep on adding "num" as long as
test@ORA92> --   the subtotal is less than "maxnum". Disregard values of "num"
test@ORA92> --   that would make the subtotal greater than "maxnum".
test@ORA92> -- To derive "dc" value:
test@ORA92> --   Sum of "num" values for ind = "N"
test@ORA92>
test@ORA92>
test@ORA92> declare
  2    maxnum   number := 15;
  3    ac       number := 0;
  4    dc       number := 0;
  5    prev     number := 0;
  6  begin
  7    FOR i IN (SELECT ind, num
  8                FROM t
  9              ORDER BY key)
10    LOOP
11       IF (i.ind = 'Y') THEN
12          ac := i.num + prev;
13          IF (ac > maxnum) THEN
14             ac := prev;
15          ELSE
16             prev := ac;
17          END IF;
18       ELSIF (i.ind = 'N') THEN
19          dc := i.num + dc;
20       END IF;
21    END LOOP;
22    dbms_output.put_line('maxnum  = '||maxnum);
23    dbms_output.put_line('ac      = '||ac);
24    dbms_output.put_line('dc      = '||dc);
25    dbms_output.put_line('prev    = '||prev);
26  end;
27  /
maxnum  = 15
ac      = 15
dc      = 17
prev    = 15
PL/SQL procedure successfully completed.
test@ORA92>
test@ORA92>Is there a way to do this processing in SQL instead ? The database version is 9i R2 (9.2.0.8.0).
Thanks and appreciate any help and/or pointers.
pratz...

Answer 1

Rob, as it was mentioned here it can be done by Hierarichal Queries, disregarding a lot of drawbacks of such a way.
SQL> with temp as (select t1.*,
  2                 (select case  when t1.ind = 'Y' and sum(num) > 15
  3                               then  null
  4                               else  sum(num)
  5                         end
  6                    from t t2
  7                  connect by level <= t1.lvl
  8                         and t2.key =
  9                             regexp_substr(t1.path, '[^/]+', 1, t1.lvl - level + 1)
10                   start with t2.key = t1.key) summa
11            from (select t.*,
12                         level lvl,
13                         sys_connect_by_path(key, '/') path,
14                         sys_connect_by_path(rn, '/') path_rn
15                    from (select t.*,
16                                 lpad(row_number() over(partition by ind order by key),2,'0') rn
17                            from t) t
18                  connect by prior key < key
19                         and prior ind = ind
20                   start with (key, ind) in
21                              (select min(key), ind from t group by ind)) t1)
22  --
23        select ind, avg(summa) keep(dense_rank first order by path_rn) max_summ
24          from (select temp.*,
25                       decode(instr(lead(path_rn) over(partition by ind order by path_rn), path_rn),1, 0, 1) flag
26                  from temp
27                 where summa is not null)
28         where flag = 1
29         group by ind
30  /
IND   MAX_SUMM
N           17
Y           15
SQL>