Databases Reference
In-Depth Information
|| ''')' ;
exception
when others
then
raise_application_error(sqlcode,sqlerrm) ;
end ;
/
Oracle 11g External Table enhancements
External Tables work the same in 10g and in 11g, so there are no differences when
working with these two versions. When working with Data Pump External Tables,
and one single row proves defective, the data set reading operation is aborted.
An enhancement in this 11g release prevents the data load aborting, thus saving
reprocessing time.
Summary
Managing data with External Tables is a means not only for mapping external
flat files as regular (but limited) tables inside the database, but also a tool to more
efficiently perform administrative tasks such as programmatically processing
database log files such as the
alert.log
or the
listener.log
files. It can be used to
easily view external XML formatted files from inside the database without actually
loading the file to the database. It can also be used as a means of unloading data in
temporary external storage to exchange data among different Oracle versions. This
particular feature allows the user to easily build an Oracle Datamart that allows the
pre-formatting and summarization of data from the source, enabling it to be directly
inserted into the target data warehouse.
The different uses an External Table has allows the user to take full advantage of
external flat files and have them loaded to the database in a very easy and convenient
way. There are limitations with External Tables, such as the lack of indexes, the full
table scans operations that must be performed even if a single row is to be accessed, the
lack of security for the flat files, and the lack of transactional control, but certainly the
advantages this concept offers overcome its disadvantages. The flexibility to manage
data in different ways makes it the default choice for data exchange operations.
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