触发器执行没有报错，但是没有生效

有没有看看哪里有问题的

create or replace trigger TRIG_SHOUFEIXM_UPDATE
after Insert Or Update
on GY_SHOUFEIXM
for each row

--declare S_BIAOZHUNBM varchar(30);
declare N_COUNT number;

-- local variables here
begin
SELECT count(*) into N_COUNT from gy_shoufeixm A WHERE A.BIAOZHUNBM IS NULL AND A.ZIFU02 IS NOT NULL;

if N_COUNT > 0 then
update gy_shoufeixm set biaozhunbm = substr(zifu02,1,20) where BIAOZHUNBM IS NULL AND ZIFU02 IS NOT NULL;
end if;

end TRIG_SHOUFEIXM_UPDATE;