Comments on: Virtual Columns

By: lkafle

lkafle — Fri, 01 Jul 2011 04:53:39 +0000

great article for oracle 11g virtual column support and its discrepancies

By: Jonathan Lewis

Jonathan Lewis — Mon, 18 Apr 2011 11:54:53 +0000

I’ve just picked up an interesting little detail about virtual columns at the MOW 2011 conference. exp doesn’t like them, and won’t export a table with a virtual column. (Still, for 11g you should be using expdp anyway.)

By: FBI oddities « Oracle Scratchpad

FBI oddities « Oracle Scratchpad — Thu, 16 Dec 2010 18:18:38 +0000

[...] you could ask to fill in further details here. For example, if you created a “genuine” virtual column in 11g using one of my “unusable” decode() expressions, and then indexed the virtual [...]

By: Predicate Problems « Oracle Scratchpad

Predicate Problems « Oracle Scratchpad — Sat, 20 Feb 2010 18:53:31 +0000

[...] to the columns) has been given the fixed “unknown range” selectivity of 5%. (In this case, the virtual column technology introduced in Oracle 11g would have helped correct the cardinality error.) But where [...]

By: Danyc

Danyc — Fri, 17 Apr 2009 20:17:59 +0000

Gents,

thank you for sharing your time & knowledge !!

Very simple and explanatory.

Kind regards,
Dani

By: Jonathan Lewis

Jonathan Lewis — Thu, 16 Apr 2009 21:53:43 +0000

Tom, The foreign key constraint is a very nice idea - I remember seeing you describe it on AskTom some time ago. As for "changing data type" - no, not quite - but you can certainly create a virtual column of the form to_date(char_col,'yyyymmdd') to deal with some of the problems of writing reports against "database independent" applications.

By: Thomas Kyte

Thomas Kyte — Thu, 16 Apr 2009 19:53:44 +0000

In addition to the extended statistics, there is the opportunity to partition by it, the opportunity to create foreign keys on them – think about that legacy system with the so called ‘intelligent key’ where the part number is the substr(primary_key,5,10). You can put a foreign key on it.

Ease of use as well – add the virtual column and you can treat it like any other column – index it, constrain it, select it, gather statistics on it, partition by it… Most everything except.. alter it’s datatype :)