Re: View from CLOB chunks
Date: Mon, 17 Nov 2008 17:21:33 +0100
Message-ID: <49219a09$0$6931$426a74cc@news.free.fr>
"Vladimir M. Zakharychev" <vladimir.zakharychev_at_gmail.com> a écrit dans le message de news:
7f32fe4b-4819-48da-aacc-4f4b0dfdde6e_at_z28g2000prd.googlegroups.com...
On Nov 14, 9:55 pm, yuri.de..._at_gmail.com wrote:
> Hello,
> Is it possible to creare a view that will split single CLOB column
> into multiple chunks of VARCHAR2 something like this:
>
> TABLE:
> ---------------------------
> ID INTEGER
> DATA CLOB
>
> into VIEW:
> --------------------------------------------------
> ID INTEGER
> CHUNK_ID INTEGER
> DATA VARCHAR(1000 char)
>
> Thanks, Yuri
Yes, it is possible. You just need a subquery that will generate sequence numbers you can use as chunk_id. For example, something like this will give you up to 1000 chunks from every CLOB:
with sqgen as
(
select level as val
from sys.dual
connect by level <= 1000
)
select id
,sqgen.val as chunk_id
,dbms_lob.substr(data, 1000, 1+(sqgen.val-1)*1000) as data
from sqgen,
myclobtable
where sqgen.val <= 1+dbms_lob.getlength(data)/1000
Note that on some older Oracle versions unfiltered CONNECT BY can't go beyond 100 levels due to some internal limits. 10.2.0.4 doesn't have such restriction, but 9.2.0.8 does.
Hth,
Vladimir M. Zakharychev
N-Networks, makers of Dynamic PSP(tm)
http://www.dynamicpsp.com
> Note that on some older Oracle versions unfiltered CONNECT BY can't go
> beyond 100 levels due to some internal limits. 10.2.0.4 doesn't have
> such restriction, but 9.2.0.8 does.
Does it?
SQL> set autotrace on
SQL> select * from (select level from dual connect by level <= 1000);
LEVEL
1
2
3
4
5
6
7
8
9
10
11
12
<snip>
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1000 rows selected.
Execution Plan
0 SELECT STATEMENT Optimizer=CHOOSE
1 0 VIEW
2 1 CONNECT BY (WITHOUT FILTERING)
3 2 TABLE ACCESS (FULL) OF 'DUAL'
Statistics
0 recursive calls
0 db block gets
3 consistent gets
0 physical reads
0 redo size
6806 bytes sent via SQL*Net to client
482 bytes received via SQL*Net from client
11 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
1000 rows processed
SQL> select * from v$version where rownum=1; BANNER
Oracle9i Enterprise Edition Release 9.2.0.8.0 - Production
1 row selected.
Regards
Michel
Received on Mon Nov 17 2008 - 10:21:33 CST