Getting the -1 node, -2 node of a hierarchy without using hierarchical q.

Question

Hi,
I have two tables similar to:
SQL> desc strdet;
Name          Type         Nullable Default Comments
COSTCENTERMS  VARCHAR2(2)  Y                        
COSTCENTERDET VARCHAR2(2)  Y                        
HIERARCHYPATH VARCHAR2(20) Y
and the table levels..
desc levels;
Name       Type         Nullable Default Comments
LEVELID    NUMBER(1)    Y                        
LEVELDESCR VARCHAR2(20) Ywith sample data as:
insert into strdet values(1,20,'1');
insert into strdet values(20,3,'1.20');
insert into strdet values(3,40,'1.20.3');
insert into strdet values(20,50,'1.20');
insert into strdet values(50,6,'1.20.50');
insert into levels values(1,'level1');
insert into levels values(2,'level2');
insert into levels values(3,'level3');
insert into levels values(4,'level4');
I constructed a query...
select costcenter , h , levelid, leveldescr,
   decode(x,3,substr(h,instr(h,'.',1,1)+1,length(costcenterms)),
            4,substr(h,instr(h,'.',1,2)+1,length(costcenterms))) l_1
from levels ,
select costcenterms, costcenter, h ,
    case when instr(h,'.',1,3)>0 then 4
         when instr(h,'.',1,2)>0 then 3
         when instr(h,'.',1,1)>0 then 2
         when instr(h,'.',1,1)=0 then 1
       end x
from
select costcenterms, costcenterdet costcenter, hierarchypath||'.'||costcenterdet h
from strdet
union
select costcenterms, costcenterms costcenter, costcenterms h
from strdet
where costcenterms not in (select costcenterdet from strdet)
where levels.levelid=x
COSTCENTER H                       LEVELID LEVELDESCR           L_1
1          1                             1 level 1             
20         1.20                          2 level 2             
3          1.20.3                        3 level 3              20
50         1.20.50                       3 level 3              20
40         1.20.3.40                     4 level 4              3
6          1.20.50.6                     4 level 4              50
6 rows selectedNow, i desire to get the following result set(with the addition of L_2 column):
COSTCENTER H                       LEVELID LEVELDESCR           L_1          L_2
1          1                             1 level 1             
20         1.20                          2 level 2             
3          1.20.3                        3 level 3              20           1
50         1.20.50                       3 level 3              20           1
40         1.20.3.40                     4 level 4              3            20
6          1.20.50.6                     4 level 4              50           20Note: I use DB 10g v.2
Thank you,
Sim

Answer 1

Hi, Sim,
So you want to find the grandparent of each node, is that it?
You have all the ancestors in the string h; you just have to pick the right one out of h.
In Oracle 10 (and up) you can use REGEXP_SUBSTR to get the n-th item from a dot-delimited string like this:
REGEXP_SUBSTR ( h
           , '[^.]+'
           , 1
           , n
           )You just want to replace n with levelid-2. However, that 4th argument (n) must be positive, so you need to do something like this:
CASE
     WHEN     levelid < 3
     THEN     NULL
     ELSE     REGEXP_SUBSTR ( h
                     , '[^.]+'
                     , 1
                     , levelid
ENDI'm curious: why don't you want to use CONNECT BY?