comparison between columns

How to compare the values between columns? I know there's a function "Greatest" in Oracle, do MS SQL have function similar to that?

And I want to create a view from a table, and one column 'll be selected from the 1 of the 4 related columns in table, say, If ColA is not null then the value is from ColA, if not , the value of the column in the view 'll be from ColB. How can i do this? Do I have to use store procedure?
( I know that's the result of poor normalization, but ... I'm not allowed to change th schema)sql/server apparently does not have anything as useful as the GREATEST function

unless someone else has a better idea, you'll have to use the CASE structure to build the equivalent --

select
(case
when a>=b and a>=c and a>=d then a
when b>=a and b>=c and b>=d then b
when c>=a and c>=b and c>=d then c
when d>=a and d>=b and d>=c then d
else a
end) as greatest

as for your other question, that's easy --

select coalesce(colA, colB) as ifAnullthenB

rudy
http://rudy.ca/|||What happens if you have Nulls?

Code:
---------------------------------------
create table #Tmp(a int, b int, c int, d int)

insert into #Tmp values(1, Null, Null, Null)
insert into #Tmp values(Null, 2, Null, Null)
insert into #Tmp values(Null, Null, 3, Null)
insert into #Tmp values(Null, Null, Null, 4)

insert into #Tmp values(5, 4, 3, 2)
insert into #Tmp values(3, 6, 4, 5)
insert into #Tmp values(4, 5, 7, 6)
insert into #Tmp values(5, 6, 7, 8)

select case
when a >= b and a >= c and a >= d then a
when b >= a and b >= c and b >= d then b
when c >= a and c >= b and c >= d then c
when d >= a and d >= b and d >= c then d
else a
end as greatest
from #Tmp

select case
when (b >= a or a is null) and (b >= c or c is null) and (b >= d or d is null) then b
when (c >= a or a is null) and (c >= b or b is null) and (c >= d or d is null) then c
when (d >= a or a is null) and (d >= b or b is null) and (d >= c or c is null) then d
else a
end as greatest
from #Tmp
---------------------------------------

Results:
---------------------------------------
greatest
----
1
NULL
NULL
NULL
5
6
7
8

greatest
----
1
2
3
4
5
6
7
8
---------------------------------------

Which is correct?