Selecting most recent date between two columns

Question

If I have a table that (among other columns) has two DATETIME columns, how would I select the most recent date from those two columns.

Example:

Answer 1

Why couldn't you use the GREATEST function?

select id, date1, date2, GREATEST( nvl(date1,date2) , nvl(date2, date1) )
from table1;

I included a NVL to ensure that NULL was evaluated correctly, otherwise if either Date1 or Date2 is null, the Greatest returns NULL.

ID  Date1       Date2       MostRecentDate
1   1/1/2008    2/1/2008    2/1/2008
2   2/1/2008    1/1/2008    2/1/2008
3   1/10/2008   1/10/2008   1/10/2008
4   -null-      2/10/2008   2/10/2008
5   2/10/2008   -null-      2/10/2008

Answer 2

select max(d) ChangeDate
from (values(@d), (@d2)) as t(d)

Answer 3

From SQL Server 2012 it's possible to use the shortcut IIF to CASE expression though the latter is SQL Standard:

SELECT ID,
       IIF(DateColA > DateColB, DateColA, DateColB) AS MostRecentDate
  FROM theTable

Answer 4

All other correct answers as already posted.

But if you are still really looking for MAX keyword then here is a way :

select ID , MAX(dt) from 
(  select Id , Date1 as dt from table1
   union  
   select ID , Date2 from table2
) d
group by d.Id

Answer 5

Other than case statement, I don't believe so...

  Select Case When DateColA > DateColB Then DateColA 
              Else DateColB End MostRecent
  From Table ... 

Answer 6

Whenever possible, use InLine functions as they suffer none of the performance issues generally associated with UDFs...

Create FUNCTION MaximumDate 
(   
@DateTime1 DateTime,
@DateTime2 DateTime
)
RETURNS TABLE 
AS
RETURN 
(
    Select Case When @DateTime1 > @DateTime2 Then @DateTime1
                Else @DateTime2 End MaxDate
)
GO 

For usage guidelines, see Here