select v=(select max(v ) from (select value1 as v union all select value2 as v union all select value3 as v --... ) a ) from t1
select (case when value1>=value2 then value1 else case when value2>=value3 then value2 else case when value3>=value4 then value3 else value4 end end end) 最大值 from max
学习一下
from (select value1 as v
union all
select value2 as v
union all
select value3 as v
--...
) a
)
from t1
value1
else case when value2>=value3 then
value2
else case when value3>=value4 then
value3
else value4 end end end) 最大值
from max