表中有A B C三列,用SQL语句实现：当A列大于B列时选择A列否则选择B列，当B列大于C列时选择B列否则选择C列

select
case
when first_name>middle_name then
case when first_name>last_name then first_name
else last_name end
else
case when middle_name>last_name then middle_name else last_name
end
end as name
from member