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<TITLE>"ALTER(TABLE") manual page</TITLE>
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<A HREF="sql.html">SQL Reference Contents</A>
<H2><A NAME="sect0" HREF="#toc0">NAME </A></H2>
alter table - add attributes to a class
<H2><A NAME="sect1" HREF="#toc1">SYNOPSIS </A></H2>
<B>alter table </B> classname
[ * ] <BR>
<tt> </tt><tt> </tt><B>add </B> [ <B>column </B> ] attname type <BR>
<B>alter table </B> classname [ * ] <BR>
<tt> </tt><tt> </tt><B>add
</B> <B>( </B> attname type <B>) </B> <BR>
<tt> </tt><tt> </tt> <BR>
<H2><A NAME="sect2" HREF="#toc2">DESCRIPTION </A></H2>
The <B>alter table</B> command causes a new
attribute to be added to an existing class, <I>classname</I>. The new attributes
and their types are specified in the same style and with the the same
restrictions as in <I>create <A HREF="table.l.html">table</I>(l)</A>
. <P>
In order to add an attribute to each
class in an entire inheritance hierarchy, use the <I>classname</I> of the superclass
and append a `*'. (By default, the attribute will not be added to any of
the subclasses.) This should <B>always</B> be done when adding an attribute to
a superclass. If it is not, queries on the inheritance hierarchy such
as select * from super* s <BR>
will not work because the subclasses will be
missing an attribute found in the superclass. <P>
For efficiency reasons, default
values for added attributes are not placed in existing instances of a
class. That is, existing instances will have NULL values in the new attributes.
If non-NULL values are desired, a subsequent <I><A HREF="update.l.html">update</I>(l)</A>
query should be
run. <P>
You must own the class in order to change its schema.
<H2><A NAME="sect3" HREF="#toc3">EXAMPLE </A></H2>
-- <BR>
-- add
the date of hire to the emp class <BR>
-- <BR>
alter table emp add column hiredate
abstime <BR>
-- <BR>
-- add a health-care number to all persons <BR>
-- (including employees,
students, ...) <BR>
-- <BR>
alter table person * add column health_care_id int4 <BR>
<H2><A NAME="sect4" HREF="#toc4">SEE
ALSO </A></H2>
create <A HREF="table.l.html">table (l)</A>
, <A HREF="update.l.html">update (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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