SQL Query for retrieving records separated by seconds - sql

Question

I am trying to write a Microsoft SQL Server query for retrieving the oldest record in which the text fields are the same, but the dates are 30 seconds or less apart. Here is an example:
My table:
RecordID TextField1 TextField2 DateField1
--------------------------------------------------------------------------------
1 SomeData1 SomeData2 9/11/2011 2:33:00pm
2 SomeData3 SomeData4 9/11/2011 2:33:15pm
3 SomeData3 SomeData4 9/11/2011 2:33:18pm
4 SomeData3 SomeData4 9/11/2011 2:42:12pm
5 SomeData1 SomeData2 9/11/2011 2:33:01pm
6 SomeData6 SomeData7 9/11/2011 2:33:01pm
7 SomeData1 SomeData2 9/12/2011 2:33:00pm
8 SomeData6 SomeData8 9/11/2011 2:33:03pm
Okay, so in this example, I want a query that will pull the rows in which TextField1=TextField1 and TextField2=TextField2 and the dates between them are 30 seconds or less (I want the oldest of the two returned). So the query, in this example, should return:
RecordID TextField1 TextField2 DateField1
--------------------------------------------------------------------------------
1 SomeData1 SomeData2 9/11/2011 2:33:00pm
2 SomeData3 SomeData4 9/11/2011 2:33:15pm
RecordID 8 is not returned because TextField2 is different.
Hopefully I explained this clearly enough. Any help would be appreciated!

Answer 1

I couldn't understand everything on your question.
This is a generic SQL query that will compare the records of you table, against the same table, looking for records with different RecordID, but equal TextField1 and TextField2.
Leave a comment if this looks like what you want and we can improve this query to get exactly what you are looking for.
UPDATED:
SELECT * FROM my_table AS t1
INNER JOIN my_table AS t2
ON (
t1.RecordID < t2.recordID
AND
DATEDIFF(second, t1.DateField1, t2.DateField1) <= 30
AND
t1.TextField1 = t2.TextField1
AND
t2.TextField2 = t1.TextField2
);

Answer 2

This returns the two records you are looking for in your example. The join between t1 and t2 returns the records that meet your criteria, and then joining to t3 returns the oldest of the rows meeting the criteria.
;
with TestCTE(RecordID, TextField1, TextField2, DateField1)
as
(
select 1, 'SomeData1', 'SomeData2', cast('9/11/2011 2:33:00pm' as datetime)
union
select 2, 'SomeData3', 'SomeData4', cast('9/11/2011 2:33:15pm' as datetime)
union
select 3, 'SomeData3', 'SomeData4', cast('9/11/2011 2:33:18pm' as datetime)
union
select 4, 'SomeData3', 'SomeData4', cast('9/11/2011 2:42:12pm' as datetime)
union
select 5, 'SomeData1', 'SomeData2', cast('9/11/2011 2:33:01pm' as datetime)
union
select 6, 'SomeData6', 'SomeData7', cast('9/11/2011 2:33:01pm' as datetime)
union
select 7, 'SomeData1', 'SomeData2', cast('9/12/2011 2:33:00pm' as datetime)
union
select 8, 'SomeData6', 'SomeData8', cast('9/11/2011 2:33:03pm' as datetime)
)
select t1.*
from TestCTE t1
join TestCTE t2 on t1.RecordID <> t2.RecordID
and t1.TextField1 = t2.TextField1
and t1.TextField2 = t2.TextField2
and datediff(second, t1.DateField1, t2.DateField1) <= 30
join
(
select TextField1, TextField2, min(DateField1) as MinDate
from TestCTE
group by TextField1, TextField2
) t3 on t1.TextField1 = t3.TextField1
and t1.TextField2 = t3.TextField2
and t1.DateField1 = t3.MinDate

Answer 3

Sounds like a simple self-join and not trying to make it more than it should. By doing the self-join and applying the group by, the following should get it done for you.
The self-join is on both text fields, and the first table's Record ID always GREATER than the one in the second table.... Then, the comparison on the date/time factor of 30 seconds.
Due to a comment from ADrift, and re-looking at the data, what I THOUGHT was a date/time stamp field on the record would always be increasing is not always the case... Slight change... Get the latest date/time for the given text1 and text2, then re-join back for rest of the details.
select
YT3.*
from
( select
YT.TextField1,
YT.TextField2,
MIN( YT.DateField1) OldestDateTime,
from
YourTable YT
Join YourTable YT2
on YT.TextField1 = YT2.TextField1
AND YT.TextField2 = YT2.TextField2
AND YT.RecordID > YT2.RecordID
AND datediff(second, YT.DateField1, YT2.DateField1) <= 30
group by
YT.TextField1,
YT.TextFIeld2 ) PreQuery
JOIN YourTable YT3
on PreQuery.TextField1 = YT3.TextField1
AND PreQuery.TextField2 = YT3.TextField2
AND PreQuery.OldestDateTime = YT3.DateField1
order by
whatever...

Answer 4

Assuming there can only be no more than two adjacent rows (those within 30 second from each other) and you are on SQL Server 2005 or later version:
WITH sampledata (RecordID, TextField1, TextField2, DateField1) AS
(
SELECT 1, 'SomeData1', 'SomeData2', CAST('20110911 14:33:00' AS datetime) UNION ALL
SELECT 2, 'SomeData3', 'SomeData4', CAST('20110911 14:33:15' AS datetime) UNION ALL
SELECT 3, 'SomeData3', 'SomeData4', CAST('20110911 14:33:18' AS datetime) UNION ALL
SELECT 4, 'SomeData3', 'SomeData4', CAST('20110911 14:42:12' AS datetime) UNION ALL
SELECT 5, 'SomeData1', 'SomeData2', CAST('20110911 14:33:01' AS datetime) UNION ALL
SELECT 6, 'SomeData6', 'SomeData7', CAST('20110911 14:33:01' AS datetime) UNION ALL
SELECT 7, 'SomeData1', 'SomeData2', CAST('20110912 14:33:00' AS datetime) UNION ALL
SELECT 8, 'SomeData6', 'SomeData8', CAST('20110911 14:33:03' AS datetime)
),
ranked AS (
SELECT
*,
rn = ROW_NUMBER() OVER (PARTITION BY TextField1, TextField2 ORDER BY DateField1)
FROM sampledata
),
SELECT
r1.RecordID,
r1.TextField1,
r1.TextField2,
r1.DateField1
FROM ranked r1
INNER JOIN ranked r2 ON r1.TextField1 = r2.TextField1
AND r1.TextField2 = r2.TextField2
AND r1.rn = r2.rn - 1
WHERE r2.DateField1 BETWEEN r1.DateField1 AND DATEADD(SECOND, 30, r1.DateField1)
Output:
RecordID TextField1 TextField2 DateField1
----------- ---------- ---------- -----------------------
1 SomeData1 SomeData2 2011-09-11 14:33:00.000
2 SomeData3 SomeData4 2011-09-11 14:33:15.000