ORA-02287 sequence number not allowed here

Question

Hello
Could someone tell my why I get this error with the following select?
create sequence dt_test_seq start with 1 increment by 1;
create table dt_test_tab (col1 number,col2 number, col3 number);
insert into dt_test_tab values(1,1,1);
insert into dt_test_tab values(1,1,1);
insert into dt_test_tab values(1,2,2);
insert into dt_test_tab values(2,2,3);
insert into dt_test_tab values(2,2,3);
select
     col1,
     col2,
     col3,
     NVL(next_val,LAG(next_val) over(partition by col1,col2 order by col1,col2))
from
     select
          col1,
          col2,
          col3,
          CASE
               WHEN  row_number() over (partition by col1,col2 order by col1,col2) = 1 THEN
                    dt_test_seq.nextval
          END next_val
     FROM
          dt_test_tab
     );I came across the problem while trying to come up with a single query answer to the post:Re: Call a function only on change of group of columns
The inner query works fine but the error comes when it is turned into an inline view and apply a function to the next_val column.
It's more out of curiosity than anything else as the answer that dmitry posted is obviously the right way to do it?
And yes, I am very bored ;-)
David

Answer 1

SQL> create function getnextval return number
2 is
3 id number;
4 begin
5 select dt_test_seq.nextval into id from dual;
6 return id;
7 end;
8 /
Function created.
SQL> edit
Wrote file afiedt.buf
1 select
2 col1,
3 col2,
4 col3,
5 CASE
6 WHEN row_number() over (partition by col1,col2 order by col1,col2) = 1 THEN
7 getnextval
8 END next_val
9 FROM
10* dt_test_tab
SQL> /
COL1 COL2 COL3 NEXT_VAL
1 1 1 99
1 1 1
1 2 2 100
2 2 3 101
2 2 3
SQL> edit
Wrote file afiedt.buf
1 select
2 col1,
3 col2,
4 col3,
5 NVL(next_val,LAG(next_val) over(partition by col1,col2 order by col1,col2)) next_v
6 from
7 (
8 select
9 col1,
10 col2,
11 col3,
12 CASE
13 WHEN row_number() over (partition by col1,col2 order by col1,col2) = 1 THEN
14 getnextval
15 END next_val
16 FROM
17 dt_test_tab
18* )
SQL> /
COL1 COL2 COL3 NEXT_V
1 1 1 105
1 1 1 105
1 2 2 106
2 2 3 107
2 2 3 107
Is it what you need ?
Rgds.
But I am afraid it's not what you need, am I not ?