Help me with my select query - sql

Question

I have this table in sql server 2005:
id student active
1 Bob 1
3 Rob 0
5 Steve 1
7 John 1
8 Mark 0
10 Dave 0
16 Nick 1
My select query returns an active student by a given id.
But I also want to return the ids of prev and next student who are active. If no prev, it will be 0 or null. Same for next.
Example: for id=5, my select would return
id student prev_id next_id
5 steve 1 7
Example: for id=7, my select would return
id student prev_id next_id
7 John 5 16
Example: for id=16, my select would return
id student prev_id next_id
16 Nick 7 0
How do I write this select query?
I have query but I just can't get the prev id correctly. It always returns the first active id.
Thanks
EDIT:
Here is the query I have right now.
select id, student,
(select top 1 id from test where id<7 and active=1) as prev,
(select top 1 id from test where id>7 and active=1) as next
from test where id=7--I used 7 just as an example. it will be a parameter

Answer 1

try something like this
SELECT ID,
Student,
( SELECT TOP 1
ID
FROM dbo.table AS pT
WHERE pT.ID < T.ID And Active = 1
ORDER BY ID DESC
) AS PrevID,
( SELECT TOP 1
ID
FROM dbo.table AS pT
WHERE pT.ID > T.ID And Active = 1
ORDER BY ID
) AS NextID
FROM dbo.table AS T

Answer 2

Working sample
DECLARE #T TABLE (id int, student varchar(10), active bit)
insert #t select
1 ,'Bob', 1 union all select
3 ,'Rob', 0 union all select
5 ,'Steve', 1 union all select
7 ,'John', 1 union all select
8 ,'Mark', 0 union all select
10 ,'Dave', 0 union all select
16 ,'Nick', 1
---- your query starts below this line
declare #id int set #id = 5
select id, student,
isnull((select top(1) Prev.id from #T Prev
where Prev.id < T.id and Prev.active=1
order by Prev.id desc),0) Prev,
isnull((select top(1) Next.id from #T Next
where Next.id > T.id and Next.active=1
order by Next.id),0) Next
from #T T
where id = #id
The ISNULLs are to return 0 when there is no match - NULL would have worked fine but your question has 0 when there is no Next.

Answer 3

You may want to take a look at Common Table Expression, a feature for only SQL Server for recursive queries, you can find a link here
But this sound like homework, and probebly not the right forum to ask it in.
Regards

Answer 4

You could use a nested query. I obviously can't test this out, but you should get the idea.
SELECT id, student ,
(SELECT C1.id FROM students S1 WHERE S1.active = 1 AND S1.id < S.id LIMIT 1) AS beforeActive,
(SELECT C2.id FROM categories S2 WHERE S2.active = 1 AND S2.id > S.id LIMIT 1) AS afterActive
FROM students S
Efficiency wise, I've no idea how well this query will perform

Answer 5

This will give you a little more control, especially since you are paginating.
WITH NumberedSet AS (
SELECT s.id,
s.student,
row_number() OVER (ORDER BY s.id) AS rownum
FROM dbo.students AS s
WHERE s.active = 1
)
SELECT cur.id,
cur.student,
isnull(prv.id,0) AS prev_id,
isnull(nxt.id,0) AS next_id
FROM NumberedSet AS cur
LEFT JOIN NumberedSet AS prv ON cur.rownum - 1 = prv.rownum
LEFT JOIN NumberedSet AS nxt ON cur.rownum + 1 = nxt.rownum
;