How to assign the max value across mulptiple fields to a single column in a select statement using MS-Access-2010 SQL?

Question

I have multiple columns in a table but I only want the highest value from the columns to be selected in a sql.

Example Info:

D1     D2     D3     D4
-----  -----  -----  -----
3      2      150    5
1      3      20     10

Output needs to be:

MaxPower
150
20

Anyone know a good way to do this? A single sql would be preferred but vba would work also.

Answer 1

How about select max(max(d1,d2), max(d3,d4)) from table ?

Answer 2

select max(v) as maggiore from (
select id,d1 as v from table
union all
select id,d2 from table
union all
select id,d3 from table
union all
select id,d4 from table
) as t
group by id