SQL Server 2008 : how to select sum of all sessions where difference between two consecutive sessions is less than 10 minutes - sql

Question

I have a table which stores chat messages for users. Every message is logged in this table. I have to calculate chat duration for a particular user.
Since there is a possibility that user is chatting at x time and after x+10 times he leaves chatting. After X+20 time, again user starts chatting. So the time period between x+10 and x+20 should not be accounted.
Table structure and sample data is as depicted. Different color represent two chat sessions for same user. As we can see that between 663 and 662 there is a difference of more than 1 hour, so such sessions should be excluded from the resultset. Final result should be 2.33 minutes.
declare #messagetime1 as datetime
declare #messagetime2 as datetime
select #messagetime1=messagetime from tbl_chatMessages where ID=662
select #messagetime2=messagetime from tbl_chatMessages where ID=659
print datediff(second,#messagetime2,#messagetime1)
Result --- 97 seconds
declare #messagetime3 as datetime
declare #messagetime4 as datetime
select #messagetime3=messagetime from tbl_chatMessages where ID=668
select #messagetime4=messagetime from tbl_chatMessages where ID=663
print datediff(second,#messagetime4,#messagetime3)
Result -- 43 seconds
Please suggest a solution to calculate duration of chat. This is one of the logic I could think of, in case any one of you has a better idea. Please share with a solution

Answer 1

first need to calculate the gap between adjacent messages, if the gap of more than 600 seconds, so the time between these messages 0
SELECT SUM(o.duration) / 60.00 AS duration
FROM dbo.tbl_chatMessages t1
OUTER APPLY (
SELECT TOP 1
CASE WHEN DATEDIFF(second, t2.messageTime, t1.messageTime) > 600
THEN 0
ELSE DATEDIFF(second, t2.messageTime, t1.messageTime) END
FROM dbo.tbl_chatMessages t2
WHERE t1.messageTime > t2.messageTime
ORDER BY t2.messageTime DESC
) o(duration)
See demo on SQLFiddle

Answer 2

Try something like this:
WITH DATA
AS (SELECT t1.*,
CASE
WHEN
Isnull(Datediff(MI, t2.MESSAGETIME, t1.MESSAGETIME), 11) > 10
THEN 0
ELSE 1
END first_ident
FROM TABLE1 t1
LEFT JOIN TABLE1 t2
ON t1.ID = t2.ID + 1),
CTE
AS (SELECT ID,
MESSAGETIME,
ID gid,
0 AS tot_time
FROM DATA
WHERE FIRST_IDENT = 0
UNION ALL
SELECT t1.ID,
t1.MESSAGETIME,
t2.GID,
t2.TOT_TIME
+ Datediff(MI, t2.MESSAGETIME, t1.MESSAGETIME)
FROM DATA t1
INNER JOIN CTE t2
ON t1.ID = t2.ID + 1
AND t1.FIRST_IDENT = 1)
SELECT GID,
Max(TOT_TIME) Tot_time
FROM CTE
GROUP BY GID
I set up a working example on SQL Fiddle. Take a look and let me know if you have any questions.

Answer 3

Here is the reasoning behind my solution. First, identify each chat that starts a chatting period. You can do this with a flag that identifies a chat that is more than 10 minutes from the previous chat.
Then, take this flag and do a cumulative sum. This sum actually serves as a grouping identifier for the chat periods. Finally, aggregate the results to get the info for each chat period.
with cmflag as (
select cm.*,
(case when datediff(min, prevmessagetime, messagetime) > 10
then 0
else 1
end) as ChatPeriodStartFlag
from (select cm.*,
(select top 1 messagetime
from tbl_chatMessages cm2
where cm2.senderId = cm.senderId or
cm2.RecipientId = cm.senderId
) as prevmessagetme
from tbl_chatMessages cm
) cm
),
cmcum as (
select cm.*,
(select sum(ChatPeriodStartFlag)
from cmflag cmf
where cm2.senderId = cm.senderId or
cm2.RecipientId = cm.senderId and
cmf.messagetime <= cm.messagetime
) as ChatPeriodGroup
from tbl_chatMessages cm
)
select cm.SenderId, ChatPeriodGroup, min(messageTime) as mint, max(messageTime) as maxT
from cmcum
group by cm.SenderId, ChatPeriodGroup;
One challenge that I may not fully understand is how you are matching between senders and recipients. All the rows in your sample data have the same pair. This is looking at the "user" from the SenderId perspective, but takes into account that in a chat period, the user could be either the sender or recipient.

Answer 4

You could use this query (here):
DECLARE #Results TABLE(
RowNum INT NOT NULL,
senderID INT NOT NULL DEFAULT(80),
recipientID INT NOT NULL DEFAULT(79),
PRIMARY KEY(RowNum,senderID,recipientID),
messageTime DATETIME NOT NULL
);
INSERT INTO #Results(RowNum,senderID,recipientID,messageTime)
SELECT ROW_NUMBER() OVER(PARTITION BY senderID,recipientID ORDER BY messageTime, ID) AS RowNum,
c.senderID,c.recipientID,c.messageTime
FROM dbo.tbl_chatMessages c;
WITH RecursiveCTE
AS(
SELECT crt.RowNum,crt.senderID,crt.recipientID,
crt.messageTime,
1 AS SessionID
FROM #Results crt
WHERE crt.RowNum=1
UNION ALL
SELECT crt.RowNum,crt.senderID,crt.recipientID,
crt.messageTime,
CASE
WHEN DATEDIFF(MINUTE,prev.messageTime,crt.messageTime) <= 10 THEN prev.SessionID
ELSE prev.SessionID+1
END
FROM #Results crt INNER JOIN RecursiveCTE prev ON crt.RowNum=prev.RowNum+1
AND crt.senderID=prev.senderID
AND crt.recipientID=prev.recipientID
)
SELECT *,
STUFF(CONVERT(VARCHAR(8), DATEADD(SECOND,x.SessionDuration,0), 114), 1,3,'') AS SessionDuration_mmss,
SUM(x.SessionDuration) OVER() AS SessionDuration_Overall,
STUFF(CONVERT(VARCHAR(8), DATEADD(SECOND,SUM(x.SessionDuration) OVER(),0), 114), 1,3,'') AS SessionDuration_Overall_mmss
FROM(
SELECT r.senderID,r.recipientID,r.SessionID,
DATEDIFF(SECOND, MIN(r.messageTime),MAX(r.messageTime)) AS SessionDuration
FROM RecursiveCTE r
GROUP BY r.senderID,r.recipientID,r.SessionID
) x
OPTION(MAXRECURSION 0);
Results:
senderID recipientID SessionID SessionDuration SessionDuration_mmss SessionDuration_Overall SessionDuration_Overall_mmss
-------- ----------- ----------- --------------- -------------------- ----------------------- ----------------------------
80 79 1 97 01:37 140 02:20
80 79 2 43 00:43 140 02:20

Answer 5

I’d focus on slight modifications in table structure and updating the chat server application code (if possible of course).
Can you have the chat server to generate new chat ID every time there is a delay between messages that is longer than X minutes? If yes then calculating chat duration will become very easy.