Comments on: Virtual Columns – 11g

By: Virtual columns revisited « Oracle Scratchpad

Virtual columns revisited « Oracle Scratchpad — Wed, 15 Apr 2009 12:24:11 +0000

[...] estimate resonably accurately how many employess have salary + nvl(commission,0) > 100000. But (until 11g, perhaps) you can’t create virtual columns unless you index them using the feature that Oracle [...]

By: avanish

avanish — Tue, 01 May 2007 06:17:11 +0000

jl, a bit late to pitch in …. but virtual columns would be very useful incases where applictaions have lot of lov kind of things, if we take the forms implementation of the lov, it would generate all the possibilites to make it a case-sensitive search, there a upper will be added on the column, in that cases, the virtual column with index would be much much better as the correct statistics would be given to the cost based optimizer.

few more things, we cannot update/insert values into the virtual column as they are derived.

but what would be the use of non-indexed virtual columns?????? what would the cost based optimizer do even if it finds the column to be selective?

By: David Aldridge

David Aldridge — Mon, 30 Oct 2006 15:08:56 +0000

In many cases the resultant change on the non-virtual column would be indeterminate anyway. UPPER(), TRUNC(), SUBSTR() etc. all spring immediately to mind.

By: Jonathan Lewis

Jonathan Lewis — Mon, 30 Oct 2006 12:56:13 +0000

Re: Jeff Kemp / Updating virtual columns:

Given the need for general purpose code, I would be surprised if anyone tried to implement such a feature, at least not in the initial versions. The scope for inconsistency and confusion seems far too high a risk.

By: Jeff Kemp

Jeff Kemp — Mon, 30 Oct 2006 11:57:08 +0000

This would be a brilliant feature.

Do you think it will support updating of those virtual columns? i.e. requiring a trigger to handle the value if such an update is logical – similar to the way we can create instead-of triggers on views which translate dml on the view to dml on the base tables…