Query to select value for max date from a varchar field containing year and month

Question

I'm having trouble selecting a value from a table that contain a varchar column in YYYY-MM format. 
ex.
Emp_id Date Cost
10264 2013-01 5.00
33644 2013-12 84.00
10264 2013-02 12.00
33644 2012-01 680.0
59842 2014-05 57.00
In the sample data above, I would like to be able to select the for each Emp_id by the max date. Ex. For Emp_id 10264, the cost should be 12.00.

Answer 1

create table test (Emp_id int, Date varchar(10), Cost decimal (6,2))
insert into test values(
10264, '2013-01', 5.00 ),
(33644, '2013-12', 84.00 ),
(10264, '2013-02', 12.00 ),
(33644, '2012-01', 680.0 ),
(59842, '2014-05', 57.00 )
Select Emp_id,[Date],Cost FROM (
select *,row_number() Over(Partition by Emp_id Order by Cast([Date]+'-1' as Datetime) Desc) rn
from test)
t
WHERE rn=1
drop table test