这句sql哪里有问题，大神帮忙看看

Question

create or replace trigger USERSS_ID before insert on USERINFO
for each row
declare
temp number;
begin
select case
when max(id)<>0 then max(id)+1
else 1
end
into temp from UserInfo;
select temp into :new.id from dual;
end;

Answer 1

sqlyog里面运行 应该会指明哪一行错误吧