RE: External tables

External tables is an access layer to O/S flat files. Consider it like an odbc to flat files.
I see it mostly used by ETL tools in data warehouse projects where we have different types of sources and the data in these sources go through series of cascaded transformations to reach the its target.

There is no need to load the data in the database to process it.

I'm sure we will have soon many access layers either by Oracle and/or others that allow us to integrate Oracle databases with the external world.

Regards,

Waleed

-----Original Message-----
Sent: Thursday, April 24, 2003 6:02 PM
To: Multiple recipients of list ORACLE-L

Another point missed so far is that
if your SQL to the external table hits
some dirty data, then it bombs out
with an Oracle error, and if you've been busy running an insert from it the next
thing that happens is a likely to be a
massive rollback.

You also have to deal with the discard/bad file (in the event that your external table definition includes a 'bad limit' and doesn't crash your process) so you haven't really got rid of much of the infrastructure that you would need if you were to use sqlldr - only the SQLLOAD command and a
couple of lines of shell to check the exit status from SQLLOAD and grep/awk the
rows-loaded count from the log.

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: 24 April 2003 19:16

> The replies so far have failed to mention that parallel loading with
> external tables is easy. With sqlloader, it ain't so easy.
>
> With external tables, it is also easy to do additional processing
via
> SQL when you load. In many cases you could avoid extra steps
required
> in sqlloader, such as loading to a temp table, then massaging your
data
> and loading to a perm table.
>
> You can skip the temp table with external tables.
>
> Jared
>
>
>

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