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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Unique(ish) sequence question, bulk collect
I don't think but you can analyze if is possible to use "bulk collect" in
your update
( see pl/sql user and reference guide)
----- Original Message -----
From: "Lord David" <DLord_at_ironmountain.co.uk>
To: <oracle-l_at_freelists.org>
Sent: Friday, February 20, 2004 4:58 AM
Subject: Unique(ish) sequence question
Hi
I need to add a sequence number to a table that is unique for *distinct* rows. I can generate the number like this: -
select rownum, x, y, z from (select distinct x, y, z from blah);
I could do it in plsql a bit like this (in practice I would have to use dbms_sql as both the table name and the list of columns is generated dynamically): -
i := 1
for rec in (select distinct x, y, z from blah) loop
update blah set id = i where x = rec.x and y = rec.y and z = rec.z
i := i + 1
end loop;
The main problem is the expense of the update (a full table scan per value of i). The tables are basically uploads from spreadsheets, so the list of columns may be quite long (10-100) and each table is only likely to be used a few times. Hence, I cannot see that there is any point in adding indexes.
Any ideas would be greatly appreciated.
--
David Lord
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