Re: Newbie question

From: Norris <johnnie_at_cooper.com.hk>
Date: 13 Sep 1999 08:32:51 GMT
Message-ID: <7ricrj$1t2a$1@adenine.netfront.net>

Can I issue SQL statement on 'virtual' table?

Rod Stewart <rod.stewart_at_afp.gov.au> wrote:

> Norris <johnnie_at_cooper.com.hk> wrote in message
> news:7ri28u$1n6g$2_at_adenine.netfront.net...
>> What is the difference between 'virtual' table and 'real' table?

> A virtual table is effectively just a select statement. To quote from
> Steven Feurerstein's Oracle PL/SQL Programming: "SELECT is called a virtual
> table because the data it produces has the same structure as a table -rows
> and columns - but it exists only for the duration of the exection of the SQL
> statement." To continue the theme then, a cursor that returns multiple
> records can pretty much be referred to as a virtual table. (Some people
> also use the term when referring to tables created in memory using PL/SQL.)
> I heard that Oracle has not introduced temporary tables before now because
> there is enough power and flexibility within PL/SQL to get by without them,
> and I tend to agree with them. Temporary tables are more expensive to use
> in terms of IO and (depending on architecture) comms because they generally
> involve the actual creation of a structure within the database. Basically a
> temporary table replicates the functionality of a virtual table, but does it
> in a more 'physical' sense. Speaking of which, I'm not sure I am making
> much so I will go home.

> HTH

> Rod J. Stewart

--
Have several nice days...

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Received on Mon Sep 13 1999 - 03:32:51 CDT