求SQL语句

[I am old man]

各位大神求帮帮老年人，求H列和I列的SQL语句，或实现方法

[I am old man]

[吉普赛的歌]

select * 
, case when H>0 then H else maxValue end as I
from(
select *
, case 取值测试方式 when 'Type1' then Type1
                              when 'Type2' then Type2
                              when 'Type3' then Type3
end as H
, case when Type1>=Type2 and Type1>=Type3 then Type1 
          when Type2>=Type1 and Type2>=Type3 then Type2
  else  Type3 end as maxValue
from t
) as tt