In SQL Server, how do I get the latest dates with multiple columns of dates?

Question

This feels like it should be an easy one. How do I get the latest of 3 dates that are in different columns

DROP TABLE #dates
CREATE TABLE #dates (mykey CHAR(10), date1 DATETIME, date2 DATETIME, date3 DATETIME)
INSERT #dates VALUES ('Key1', '1/1/2015', '2/1/2015', '3/1/2105')
INSERT #dates VALUES ('Key2', '1/2/2015', '4/2/2015', '3/2/2105')
INSERT #dates VALUES ('Key3', '1/3/2016', '4/3/2015', '3/3/2105')

select mykey, ?? AS 'Latest Date' from #dates

I would like the result to be:

mykey       Latest Date
Key1        2105-03-01 00:00:00.000
Key2        2015-04-02 00:00:00.000
Key3        2016-01-03 00:00:00.000

Answer 1

Probably the easiest way in SQL Server is to use cross apply:

select d.*, m.maxdate
from #dates d cross apply
     (select max(dte) as maxdate
      from (values (date1), (date2), (date3)) as v(dte)
     )  m;