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<TITLE>"CREATE(VIEW") manual page</TITLE>
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<A HREF="sql.html">SQL Reference Contents</A>
<H2><A NAME="sect0" HREF="#toc0">NAME </A></H2>
create view - construct a virtual class
<H2><A NAME="sect1" HREF="#toc1">SYNOPSIS </A></H2>
<B>create view </B> view_name
<B>as </B> <BR>
<tt> </tt><tt> </tt><B>select </B> expression1 [<B>as </B> attr_name1] <BR>
<tt> </tt><tt> </tt>{, expression_i [<B>as </B> attr_namei]}
<BR>
<tt> </tt><tt> </tt>[<B>from </B> from.last] <BR>
<tt> </tt><tt> </tt>[<B>where </B> qual] <BR>
<H2><A NAME="sect2" HREF="#toc2">DESCRIPTION </A></H2>
<B>create view</B> will define
a view of a class. This view is not physically materialized; instead the
rule system is used to support view processing as in [STON90]. Specifically,
a query rewrite retrieve rule is automatically generated to support retrieve
operations on views. Then, the user can add as many update rules as desired
to specify the processing of update operations to views. See [STON90]
for a detailed discussion of this point.
<H2><A NAME="sect3" HREF="#toc3">EXAMPLE </A></H2>
-- <BR>
--create a view consisting
of toy department employees <BR>
-- <BR>
create view toyemp as <BR>
<tt> </tt><tt> </tt>select e.name <BR>
<tt> </tt><tt> </tt>from emp e <BR>
<tt> </tt><tt> </tt>where e.dept = 'toy' <BR>
-- <BR>
--Specify deletion semantics for toyemp
<BR>
-- <BR>
create rule example1 as <BR>
<tt> </tt><tt> </tt>on delete to toyemp <BR>
<tt> </tt><tt> </tt>do instead delete emp
<BR>
<tt> </tt><tt> </tt>where emp.oid = current.oid <BR>
<H2><A NAME="sect4" HREF="#toc4">SEE ALSO </A></H2>
create <A HREF="table.l.html">table(l)</A>
, create <A HREF="rule.l.html">rule(l)</A>
,
<P>
<HR><P>
<A NAME="toc"><B>Table of Contents</B></A><P>
<UL>
<LI><A NAME="toc0" HREF="#sect0">NAME</A></LI>
<LI><A NAME="toc1" HREF="#sect1">SYNOPSIS</A></LI>
<LI><A NAME="toc2" HREF="#sect2">DESCRIPTION</A></LI>
<LI><A NAME="toc3" HREF="#sect3">EXAMPLE</A></LI>
<LI><A NAME="toc4" HREF="#sect4">SEE ALSO</A></LI>
</UL>
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