
> trigger.  It is
    up to the trigger to work out what to update based on the old and
    new row values.</P
><P
>    Another possibility is for the user to define <TT
CLASS="LITERAL"
>INSTEAD</TT
>
    rules that specify substitute actions for <TT
CLASS="COMMAND"
>INSERT</TT
>,
    <TT
CLASS="COMMAND"
>UPDATE</TT
>, and <TT
CLASS="COMMAND"
>DELETE</TT
> commands on
    a view. These rules will rewrite the command, typically into a command
    that updates one or more tables, rather than views. That is t