y.
        </P
></LI
><LI
><P
>            The join trees show a simple join between <TT
CLASS="LITERAL"
>t1</TT
> and <TT
CLASS="LITERAL"
>t2</TT
>.
        </P
></LI
></UL
><P>
   </P
><P
>    The consequence is, that both query trees result in similar
    execution plans: They are both joins over the two tables. For the
    <TT
CLASS="COMMAND"
>UPDATE</TT
> the missing columns from <TT
CLASS="LITERAL"
>t1</TT
> are added to
    the target list by the planner and the final query tree will read
    as:

</