Conditional formatting on MAX value row - sql

Question

Below is a table:
Paration by ID & capture the row of MAX value when Role = Red
ID Role HistID Date Style
1 Yellow 101 1/1/17 M
1 Red 101 1/2/17 F
1 Red (Null) 1/5/17 C
2 Blue 101 5/1/17 a
2 Yellow 201 4/1/17 b
2 Red 301 5/5/17 C
3 Yellow (Null)
Referece the below rows:
ID Role HistID Date Style
1 Red (Null) 1/5/17 c
2 Red 301 5/5/17 c
Now based off those rows apply a condition.
WHEN HistID IS NOT NULL and Style = C THEN 'Assigned'
ELSE'Unassigned'
END Status
Output:
ID Role HistID Date Style Status
1 Yellow 101 1/1/17 M Unassigned
1 Red 101 1/2/17 F Unassigned
1 Red (Null) 1/5/17 C Unassigned
2 Blue 101 5/1/17 a Assigned
2 Yellow 201 4/1/17 b Assigned
2 Red 301 5/5/17 C Assigned
3 Yellow (Null) Unassigned
Not so much the answer here, I would like understand and learn the syntax behind applying MAX , Case Expression and Keep clause.

Answer 1

Use window functions:
select t.*,
(case when matches_flag > 0 then 'Assigned' else 'Unassigned' end) as status
from (select t.*,
sum(case when role = 'Red' and histid is not null and style = 'C' then 1 else 0 end) over
(partition by id) as matches_flag
from t
) t;
EDIT:
The subquery is not actually needed. I just think it makes the logic easier to follow. You can do:
select t.*,
(case when sum(case when role = 'Red' and histid is not null and style = 'C' then 1 else 0 end) over (partition by id) > 0
then 'Assigned'
else 'Unassigned'
end) as status
from t;