compare next record in the same table sql - sql

Question

I have a table having 2 columns trans_date and amount.
I want to a query that give me the amount if the transdate diff of a record and the next record is 1 day or same day.
explanation:
AMOUNT TRANS_DATE
2645 2011-05-11 20:57:27.000
2640 2011-05-12 00:00:00.000
2645 2011-05-15 18:01:11.000
2645 2011-06-15 18:27:45.000
2645 2011-06-16 17:06:33.000
2645 2011-06-18 15:19:19.000
2645 2011-06-23 15:42:18.000
the query should show me only
AMOUNT TRANS_DATE
2645 2011-05-11 20:57:27.000
2640 2011-05-12 00:00:00.000
2645 2011-05-15 18:01:11.000
2645 2011-06-15 18:27:45.000
2645 2011-06-16 17:06:33.000
all i have tried is
select DATEDIFF(DAY,a.TRANS_DATE,b.TRANS_DATE) from FIN_AP_PAYMENTS a inner join ( select * from (select a.*,rank() over (order by id) as ra from FIN_AP_PAYMENTS a, FIN_AP_PAYMENTS b )tbl )
select a.TRANS_DATE,b.TRANS_DATE,rank() over (order by a.id) as ra1,rank() over (order by b.id) as ra2 from FIN_AP_PAYMENTS a,FIN_AP_PAYMENTS b
select DATEDIFF(day,tbl.TRANS_DATE,tbl2.TRANS_DATE) from (select a.*,rank() over (order by id) as ra from FIN_AP_PAYMENTS a) tbl inner join (select a.*,rank() over (order by a.id) as ra1 from FIN_AP_PAYMENTS a ) tbl2 on tbl.id=tbl2.id

Answer 1

Use lead() and lag() to get the next and previous values. Then check the timing between them for filtering:
select t.amount, t.trans_date
from (select t.*, lead(trans_date) over (order by trans_date) as next_td,
lag(trans_date) over (order by trans_date) as prev_td
from FIN_AP_PAYMENTS t
) t
where datediff(second, prev_td, trans_date) < 24*60*60 or
datediff(second, trans_date, next_trans_date) < 24*60*60;
EDIT:
In SQL Server 2008, you can do this using outer apply:
select t.amount, t.trans_date
from (select t.*, tlead.trans_date as next_td,
tlag.trans_date as prev_td
from FIN_AP_PAYMENTS t outer apply
(select top 1 t2.*
from FIN_AP_PAYMENTS t2
where t2.trans_date < t.trans_date
order by trans_date desc
) tlag outer apply
(select top 1 t2.*
from FIN_AP_PAYMENTS t2
where t2.trans_date > t.trans_date
order by trans_date asc
) tlead
) t
where datediff(second, prev_td, trans_date) < 24*60*60 or
datediff(second, trans_date, next_trans_date) < 24*60*60;

Answer 2

Pre SQL Server 2012 you can use a combination of ROW_NUMBER and self joins instead of LEAD and LAG.
Example
WITH Example AS
(
SELECT
ROW_NUMBER() OVER (ORDER BY Trans_Date) AS rn,
r.*
FROM
(
VALUES
(2645, '2011-05-11 20:57:27.000'),
(2640, '2011-05-12 00:00:00.000'),
(2645, '2011-05-15 18:01:11.000'),
(2645, '2011-06-15 18:27:45.000'),
(2645, '2011-06-16 17:06:33.000'),
(2645, '2011-06-18 15:19:19.000'),
(2645, '2011-06-23 15:42:18.000')
) AS r(Amount, Trans_Date)
)
SELECT
curr.*,
FROM
Example AS curr
LEFT OUTER JOIN Example AS prv ON prv.rn = curr.rn - 1
INNER JOIN Example AS nxt ON nxt.rn = curr.rn + 1
WHERE
DATEDIFF(DAY, curr.Trans_Date, nxt.Trans_Date) IN (0, 1)
OR DATEDIFF(DAY, prv.Trans_Date, curr.Trans_Date) IN (0, 1)
;
The CTE allows you to reuse the row number multiple times. The row number provides a sequence for the self joins. The joins allow to you see the previous and next values on the same row, for comparison.
The output of this query doesn't match your example, see my question in the comments for more on this.
I'm not sure that telling people, who are giving up their time to help you, what you are / are not here to discuss is a good idea. It certainly made me think twice before posting.