# More on view updates and inverse views

From: Tegiri Nenashi <tegirinenashi_at_gmail.com>

Date: Sun, 6 Sep 2009 12:06:06 -0700 (PDT)

Message-ID: <859006da-471c-4272-8205-139afcd62e1a_at_i18g2000pro.googlegroups.com>

Suppose we have views u, w defined as relational expressions over base tables x, y, z:

Date: Sun, 6 Sep 2009 12:06:06 -0700 (PDT)

Message-ID: <859006da-471c-4272-8205-139afcd62e1a_at_i18g2000pro.googlegroups.com>

Suppose we have views u, w defined as relational expressions over base tables x, y, z:

u = f(x,y,z)

w = g(x,y,z)

Let's assume this system of equations is invertible, that is we can solve it and express x, y, z as functions of u, w:

x = r(u,v) y = s(u,v) z = t(u,v)

Then, the system of views u,w is updatable. Given the new database state reflected in the relations u, w, we can calculate base relations by leveraging above expressions. One can object that it wouldn't be a practical solution; on the plus side, however, increments and decrements never enter the picture! Received on Sun Sep 06 2009 - 21:06:06 CEST