Getting unique or primary key columns for a given table

declare @table_name nvarchar(50)

set @table_name = 'Sample'

select
    c.name as [Column_Name],
    kc.name as [Constraint_Name],
    object_name(c.object_id) as [Table_Name]
from sys.columns c
join sys.key_constraints kc
 on (c.column_id = kc.unique_index_id and c.object_id = kc.parent_object_id)
where kc.type='UQ' -- or kc.type = 'PK'
and c.object_id = object_id(@table_name)