Question

table1
    - date1 datetime not null
    - date2 nvarchar null

I want to get the latest date of this two.

select date1, date2, 
(CASE WHEN date1 > CAST(date2 as DateTime) THEN date1 ELSE date2 END) as DateTime) as LatestDate
from table1

please note that date2 can be null. in this case, date1 win.

Answer 1

SELECT date1, date2,  
CASE 
  WHEN date1 > CAST(ISNULL(date2,'1900-01-01') as DateTime) THEN 
     date1 
  ELSE 
    CAST(date2 as DateTime) 
END  as LatestDate 
FROM table1