How to get the previous record in the select statement

Question

I am trying to update the parent part number as a parent for component part number. I can assign the main part with level 1 as a parent and it looks like this.
PART_NUMBER     PART_LEVEL     PART_PARENT
1140000000T     3     1140001755L
1140001755D     2     1140001755L
1140001755L     1     
A1010000139     5     1140001755L
A1010015001     4     1140001755L
A1010000139I     4     1140001755L
A40210062     2     1140001755L
A1010001579     4     1140001755L
but, I need to assign the previous level part as the parent part instead of level 1. I can add a new column to store this value. I need the structure as
PART_NUMBER     PART_LEVEL     PART_PARENT
1140001755L     1     
1140001755D     2     1140001755L
A40210062     2     1140001755L
1140000000T     3     A40210062
A1010015001     4     1140000000T
A1010000139I     4     1140000000T
A1010001579     4     1140000000T
A1010000139     5     A1010001579
We might have multiple parts at the same level, so I need to make sure that correct parent is assigned to the part. Anybody has any idea?
Thanks

Answer 1

spooHi,
How to do that depends on your data.
Post a little sample data (CREATE TABLE and INSERT statements) and the results you want from that data (formatted, within \ tags), if it's not the reuslts you already posted.   If you can show what your problem is using commonly available tables (like scott.emp), then you don't have to post any sample data; just the results.
Post your existing query, too;.  Always say what version of Oracle you're using.
It looks like you're currently doing something like this:SELECT     ename
,     LEVEL
,     CONNECT_BY_ROOT ename     AS root_ename
FROM     scott.emp
START WITH     mgr     IS NULL
CONNECT BY     mgr     = PRIOR empno
which produces this output:ENAME LEVEL ROOT_ENAME
KING 1 KING
JONES 2 KING
SCOTT 3 KING
ADAMS 4 KING
FORD 3 KING
SMITH 4 KING
BLAKE 2 KING
ALLEN 3 KING
WARD 3 KING
MARTIN 3 KING
TURNER 3 KING
JAMES 3 KING
CLARK 2 KING
MILLER 3 KING
where the last column shows the ancestor *farthest* above the current row.
If I understand you, you want to have output that shows the *nearest* anacestor, like this:NAME LEVEL PARENT_ENA
KING 1
JONES 2 KING
SCOTT 3 JONES
ADAMS 4 SCOTT
FORD 3 JONES
SMITH 4 FORD
BLAKE 2 KING
ALLEN 3 BLAKE
WARD 3 BLAKE
MARTIN 3 BLAKE
TURNER 3 BLAKE
JAMES 3 BLAKE
CLARK 2 KING
MILLER 3 CLARK
You can do that by changing a single line:SELECT     ename
,     LEVEL
,     PRIOR ename          AS parent_ename          -- Changed
FROM     scott.emp
START WITH     mgr     IS NULL
CONNECT BY     mgr     = PRIOR empno