我有一个数据表test，testnum（int）和testtext（varchar），想写一个触发器来满足当testnum大于0少于20的时候，testtext显示“你好”，如果testnum大于20的时候testtext就显示“再见”，我想用update触发器，因为testnum是由另外的表控制的。
应该还需要insert触发器吧
create trigger it_test on test
instead of insert
as
insert into test(testnum,testtext)
select testnum,case when testnum between 0 and 20 then '你好'
when testnum > 20 then '再见'
end
from inserted
go
create trigger tu_test on test
for update
as
if update(testnum) and exists(select 1 from inserted i,deleted d where i.testnum<>d.testnum)
begin
update test
set testtext=case when testnum between 0 and 20 then '你好'
when testnum > 20 then '再见'
end
end
http://community.csdn.net/Expert/topic/5476/5476519.xml?temp=.4222528