s follow simple visibility rules: none of
       the changes made by a statement are visible to statement-level
       triggers that are invoked before the statement, whereas all
       modifications are visible to statement-level <TT
CLASS="LITERAL"
>AFTER</TT
>
       triggers.
      </P
></LI
><LI
><P
>       The data change (insertion, update, or deletion) causing the
       trigger to fire is naturally <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>not</I
></SPAN
> visible
       to SQL commands executed