Generating sequence for group by condition

Question

I have a table with the Name Table_Depts.
SQL> DESC Table_depts
Name varchar2(10)
Deptno number(5)
Loc varchar2(10)
SQL> Select * from Table_depts;
NAME ---- Sale
DEPTNO ---- null
LOC --- boston
NAME ---- Sale
DEPTNO ---- null
LOC --- boston
NAME ---- Purchase
DEPTNO ---- null
LOC --- boston
NAME ---- Admin
DEPTNO ---- null
LOC --- NewJS
NAME ---- Admin
DEPTNO ---- null
LOC --- boston
NAME ---- Admin
DEPTNO ---- null
LOC --- Mums
Note that Deptno is null. I want to update deptno column.
NAME ---- Sale
DEPTNO ---- 1
LOC --- boston
NAME ---- Sale
DEPTNO ---- 2
LOC --- boston
NAME ---- Purchase
DEPTNO ---- 1
LOC --- boston
NAME ---- Admin
DEPTNO ---- 1
LOC --- NewJS
NAME ---- Admin
DEPTNO ---- 2
LOC --- boston
NAME ---- Admin
DEPTNO ---- 3
LOC --- Mums
That means For sale we have (deptno 1 and 2) and
for Purchase we have (deptno 1)
and for Admin we have (deptno 1,2,3)
This output this based on group by of names and
the deptno is sequencely updates... but it again starts
when it gets new name that is (Sale have 1,2,3) and
(purchase have 1) and so on...
Thanks and regards
Sarfaraz Enayat

Answer 1

what for is MERGE here?
simple update is enough:Here is the reason for MERGE. Please note the numbers printed bold:
merge into x
using (select id
            , deptno
            , row_number() over (partition by name order by loc) rn
         from x
      ) r
  on (r.id = x.id)
when matched
then
    update set deptno = rn
when not matched then
    insert values (null,null,null,null)
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.01          0          0          0           0
Execute      1      0.01       0.00          0          6          7           6
Fetch        0      0.00       0.00          0          0          0           0
total        2      0.01       0.02          0          6          7           6
Misses in library cache during parse: 1
Optimizer goal: CHOOSE
Parsing user id: 9833
Rows     Row Source Operation
      2  MERGE
      6   VIEW
      6    HASH JOIN OUTER
      6     VIEW
      6      WINDOW SORT
      6       TABLE ACCESS FULL X
      6     TABLE ACCESS FULL X
update x
   set deptno =
       ( select rn
           from ( select t.*
                       , row_number() over (partition by name order by id) rn
                    from x t
                ) tt
          where tt.id = x.id
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.01       0.00          0          0          0           0
Execute      1      0.00       0.00          0         21         14           6
Fetch        0      0.00       0.00          0          0          0           0
total        2      0.01       0.00          0         21         14           6
Misses in library cache during parse: 1
Optimizer goal: CHOOSE
Parsing user id: 9833
Rows     Row Source Operation
      0  UPDATE
      6   TABLE ACCESS FULL OBJ#(2716057)
      6   VIEW
     36    WINDOW SORT
     36     TABLE ACCESS FULL OBJ#(2716057)
********************************************************************************You can imagine what the numbers are for larger tables ...
Regards,
Rob.