SQL> select * from t order by p,n;

        ID          P          N
---------- ---------- ----------
         1          1          1
         2          1          2
         3          1          3
         4          2          1
         5          2          2
         6          2          3
         7          2          4

7 rows selected.

SQL> print :t_in

      T_IN
----------
         1

SQL> MERGE INTO t
  2  USING (
  3  select
  4    k.*
  5   ,row_number() over (partition by p order by srt,n) rn
  6  from
  7   (select id,p,n,1 srt from t where p=:t_in --старые книги
  8    union all
  9    select id,:t_in,n,0 srt from t where id in (4,5) -- добавленные (0- в начало  2- в конец)
 10    union all
 11    select id,p,n,1 srt from t where id not in (4,5)
 12                        and p=(select min(p) from t where id in (4,5)) -- без снятих
 13   ) k
 14  ) z
 15  ON (t.ID = z.ID)
 16  WHEN MATCHED
 17  THEN UPDATE
 18   SET t.p=z.p, n=z.rn
 19  /

7 rows merged.

SQL> select * from t order by p,n;

        ID          P          N
---------- ---------- ----------
         4          1          1
         5          1          2
         1          1          3
         2          1          4
         3          1          5
         6          2          1
         7          2          2

7 rows selected.

SQL> rollback;

Rollback complete.

SQL> ed
Wrote file afiedt.buf

  1  MERGE INTO t
  2  USING (
  3  select
  4    k.*
  5   ,row_number() over (partition by p order by srt,n) rn
  6  from
  7   (select id,p,n,1 srt from t where p=:t_in --старые книги
  8    union all
  9    select id,:t_in,n,2 srt from t where id in (4,5) -- добавленные (0- в начало  2- в конец)
 10    union all
 11    select id,p,n,1 srt from t where id not in (4,5)
 12                        and p=(select min(p) from t where id in (4,5)) -- без снятих
 13   ) k
 14  ) z
 15  ON (t.ID = z.ID)
 16  WHEN MATCHED
 17  THEN UPDATE
 18*  SET t.p=z.p, n=z.rn
SQL> /

7 rows merged.

SQL> select * from t order by p,n;

        ID          P          N
---------- ---------- ----------
         1          1          1
         2          1          2
         3          1          3
         4          1          4
         5          1          5
         6          2          1
         7          2          2

7 rows selected.

SQL> rollback;

Rollback complete.

SQL>