create or replace trigger name
after insert or update or delete on table1
FOR EACH ROW
begin
CASE
WHEN inserting THEN
update table2 set field2 = select sum(*) from table1;
WHEN updating THEN
update table2 set field2 = select sum(*) from table1;
WHEN deleting THEN
update table2 set field2 = select sum(*) from table1;
END CASE;
end;