Re: Newbie question

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 Received on Mon Sep 13 1999 - 01:59:41 CDT