SQL tree data struct(1): adjacency list (id, parentid)

declare @tree table(emp varchar(30), boss varchar(30))
insert @tree
select 'Albert', NULL
union all select 'Bert', 'Albert'
union all select 'Chuck', 'Albert'
union all select 'Donna', 'Chuck'
union all select 'Eddie', 'Chuck'
union all select 'Fred', 'Chuck'

select * from @tree