Update a column using a connect by or other for hierachical relationships

Question

I have a column which represents the 'order' of which a record loaded out of a table.
This 'order' is coming in wrong.
I know, because of a relatoinship between two of the columns what the correct order should be.
So for example if I do this:
select transid, laborcode, supervisorfrom enclabor_iface
connect by prior laborcode = supervisor
start with supervisor = 0;
I get all the records in the correct order... but of course I'd like to figure out how to use this in an update statement to update the transid columns, which is the order.
Can someone tell me if this is possible, and if so, how to do so?
I have tried a few things with no luck yet, as the attempt took over 15 minutes to run so I thought I had coded it badly.
thanks
Jeff

Answer 1

Hi, Jeff,
Sure, that's possible.
The ROWNUM pseudo-column is assigned as the CONNECT BY clause (including ORDER SIBLINGS BY) is being applied, so you can use ROWNUM to capture the hierarchical order.
I don't have a copy of your table, so I'll use scott.emp to illustrate:
SELECT       ename, empno, mgr
,       ROWNUM          AS r_num
FROM       scott.emp
START WITH     mgr     IS NULL
CONNECT BY     mgr     = PRIOR EMPNO
ORDER SIBLINGS BY     ename
;Output:
ENAME      EMPNO   MGR      R_NUM
KING        7839                1
BLAKE       7698  7839          2
ALLEN       7499  7698          3
JAMES       7900  7698          4
MARTIN      7654  7698          5
TURNER      7844  7698          6
WARD        7521  7698          7
CLARK       7782  7839          8
MILLER      7934  7782          9
JONES       7566  7839         10
FORD        7902  7566         11
SMITH       7369  7902         12
SCOTT       7788  7566         13
ADAMS       7876  7788         14The default CONNECT BY ordering guarantees that (for example) all of BLAKEs descendants will come after BLAKE and before anyone who is not a descendant of BLAKE. However, it says nothing about whether BLAKE will come before JONES, or vice-versa. If that's important, use ORDER SIBLINGS BY.
To store those numbers in your table, do the query above in a MERGE statement.
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) for all tables involved, and also post the results you want from that data.
If you're asking about a DML statement, such as MERGE, the sample data will be the contents of the table(s) before the DML, and the results will be state of the changed table(s) when everything is finished.
Explain, using specific examples, how you get those results from that data.
Always say which version of Oracle you're using.
Edited by: Frank Kulash on Feb 7, 2012 11:46 AM