Simple max() function and inner join T-SQL - sql

Question

I have simple table which puzzles me:
CREATE TABLE [dbo].[T3]
(
[id] [int] IDENTITY(1,1) NOT NULL,
[S_Id] [int] NULL,
[P_Id] [int] NULL,
[level] [int] NULL,
[Path] [nvarchar](255) NULL
) ON [PRIMARY]
In the table is data
id S_Id P_Id level Path
------------------------------------
1 218252 218231 1 218231
2 218271 218252 1 218252
3 218271 218252 2 218231-218252
EDIT:
I try to get the
ID, S_ID, P_ID, level, Path
on maximum length of column Path.
It should return id 3.
If I try to get max len from path like this:
select
b.id, a.p_id, a.s_id,
max(len(a.path)) as Path,
a.path
from
t3 a, t3 b
where
b.id = a.id
group by
a.p_id , a.s_id, b.id , a.path
order by
1
I get all the data, not just row with id 3, why ?

Answer 1

If you only want the max path record... Correct me if I'm wrong.
;WITH tmp AS (select TOP 1 id from #TaskTask3 ORDER BY LEN(path) DESC)
select t.*
from #TaskTask3 t
inner join tmp on tmp.id = t.id
Updates
;WITH tmp AS (select id, row_number() over (partition by S_Id, P_Id order by len(path) DESC) as rn from #TaskTask3)
select t.*
from #TaskTask3 t
inner join tmp on tmp.id = t.id
WHERE tmp.rn = 1

Answer 2

I tried to keep it simple....There are other methods (mentioned already) but I think you need to start slow... :)
declare #maxLen int
select #maxLen = max(len(path))
from t3
select * from t3
where len (path) = #maxLen

Answer 3

To put weePee's answer in a simple way,you can use the following query:
select id,s_id,p_id,level from t3 where len(path)= (select max(len(path)) from t3)
This is what I used to create and insert into table t3:
CREATE TABLE [dbo].[T3]
(
[id] [int] IDENTITY(1,1) NOT NULL,
[S_Id] [int] NULL,
[P_Id] [int] NULL,
[level] [int] NULL,
[Path] [nvarchar](255) NULL
) ON [PRIMARY]
insert into t3 (s_id,p_id,level,path) values (218252,218231,1,'218231'),(218271,218252,1,'218252'),(218271,218252,2,'218231-218252')