Creating a hierarchical tree

Question

Hi,
I have 3 tables t1, t2, t3.
t1 is the master of t2.
t2 is the master of t3.
Data in t1:
seq      name
1          m
2          g
Date in t2
seq  t1_seq    name
1         1         mani
2         1         julia
3         2        kali
4         2        mali
5         2         toli
data  in t3
seq  t2_seq    title
1         1         manager
2         1         clerk
3         2        developer
4         2        clerk
5         2         salesman
6         4        manager
7         4        clerk
8         2        developer
9         3        clerk
10        3         developer---------------------------------------------------------------------------------------------------
I want the data to print for t1 seq = 1 in the following way:
mani
       manager
       clerk
julia
     developer
      clerk
      salesmanI have written the code in the following way but it was not displaying the result. Please correct me where i am going wrong.
Note: the data should be displayed in hierarchical tree fashion.
select 1, level, t3.title
from t2, t3
connect by prior t2.seq = t3.t2_seq and t2.t1_seq = 1
start with t3.t2_seq IS NOT NULL;
Thanks in advance,

Answer 1

Hi,
CONNECT BY queries operate on a table (or result set) where every row represents a node.
In your tables, all the nodes on level 1 are in table t2, but all the nodes on level 2 are in table t3, so you have to do a UNION to make them all appear in a single in-line view.
WITH
u     AS
(     -- Begin in-line view u, UNION of t2 and t3 as hierarchy
     SELECT seq     AS node_id,     -1     AS parent_id,     name          AS label
     FROM t2
     WHERE t1_seq = 1
UNION ALL
     SELECT NULL     AS node_id,     t2_seq     AS parent_id,     '   ' || title     AS label
     FROM t3
)     -- End in-line view u, UNION of t2 and t3 as hierarchy
SELECT     label
FROM     u
START WITH     parent_id     = -1
CONNECT BY     parent_id     = PRIOR node_id
;This assumes that -1 is never used as a key in your tables.
Instead of using LEVEL and L- or RPAD to indent children under their parents, I relied on the fact that all the rows from the same table would be at the same, fixed LEVEL. It might be more efficient to continue that reasoning farther, and consider this problem not as a CONNECT BY query at all, but a master-detail query:
WITH
v2     AS
(     -- Begin in-line view v2, relevant data from t2
SELECT     seq          AS t2_seq
,     -1          AS t3_seq
,     name          AS label
FROM     t2
WHERE     t1_seq = 1
)     -- End in-line view v2, relevant data from t2
SELECT     label,                    t2_seq,     t3_seq
FROM     v2
UNION     
SELECT     '   ' || title     AS label,     t2_seq,     seq AS t3_seq
FROM     t3
WHERE     t2_seq IN (SELECT t2_seq FROM v2)
ORDER BY     t2_seq
,          t3_seq
;This second query produces the same lable column as the CONNECT BY query above, plus two other columns needed for sorting:
LABEL             T2_SEQ     T3_SEQ
mani                   1         -1
   manager             1          1
   clerk               1          2
julia                  2         -1
   developer           2          3
   clerk               2          4
   salesman            2          5
   developer           2          8You can hide the extra columns with the SQL*Plus "COLUMN ... NOPRINT" command, or you can use another in-line view. (The sorting columns only have to be in the result set of the UNION query itselt.)
In my results, julia appears with the developer role twice. That seems correct if table t3 includes both of these rows:
3         2        developer
8         2        developer