Sql Query : Next Last Rows - sql

Question

I have tables Customer and Calls like this:
Customers table:
CustomerId : uniqueidentifier
BusinessName : nvarchar(MAX)
Calls table:
CallId : uniqueidentifier
CallDate :datetime
CustomerId: uniqueidentifier
Status: int (call has been answered or no)
I want to get all the customers with last called and next call columns.
Last Called is the last call where status = 1. Next Call is the call where status = 0 and the Calldate > now date. Null if they do not have any. This is a non working example just to show the format
Select *
From Customers,
Calls.CallId as LastCalledId
Calls.CallDate as LastCalledDate
Calls.CallId as NextCallId
Calls.CallDate as NextCallDate
LEFT JOIN
Calls ON Customers.CustomerId = Calls.CustomerId
How can I do this?

Answer 1

Is this what you mean?
Update
select c.id
, lastcall.calldate
, lastcall.id
, firstcall.calldate
, firstcall.id
from #customers c
outer apply (select top 1 calls.calldate, calls.id from #calls calls where calls.custid = c.id and calldate < getdate() order by calldate desc) lastcall(calldate, id)
outer apply (select top 1 calls.calldate, calls.id from #calls calls where calls.custid = c.id and calldate >= getdate() order by calldate asc) firstcall(calldate, id)
original answer:
select c.id
, answered.calldate LastCalledDate
, answered.id LastCalledID
, unaswered.calldate NextCalledDate
, unaswered.id NextCalledID
from #customers c
left join #calls answered ON answered.custid = c.id AND status = 1
left join #calls unaswered ON unaswered.custid = c.id AND unaswered.status = 0 and unaswered.calldate > getdate()

Answer 2

You can use WHERE clause in LEFT JOIN for getting required data rows.Here you can use where clause with Calls.status = 0 or 1 (as per your requirement)

Answer 3

Since you didn't provide DDL and DML for sample data I couldn't test my answer, so It's not guaranteed to produce the desired results.
Having said that, here is my attempt that should work on versions 2008 or higher.
Using a cte to calculate the last answered call for each customer (assuming calldate is unique) and a couple of left joins I came up with this:
;WITH LastCall AS
(
SELECT CustomerId,
CallId,
CallDate
FROM Calls t0
WHERE [Status] = 1
AND CallDate =
(
SELECT MAX(CallDate)
FROM Calls t1
WHERE [Status] = 1
AND t1.CustomerId = t0.CustomerId
)
)
SELECT cu.CustomerId,
cu.Name,
lc.CallId as LastCalledId,
lc.CallDate as LastCalledDate,
nc.CallId as NextCallId,
nc.CallDate as NextCallDate
FROM Customers as cu
LEFT JOIN LastCall lc ON cu.CustomerId = lc.CustomerId
LEFT JOIN Calls nc ON cu.CustomerId = nc.CustomerId AND nc[Status] = 0 AND nc.CallDate > GETDATE()
Please note that for versions 2012 and higher you might be able to use FIRST_VALUE or LAST_VALUE built in functions.

Answer 4

You can use AND in join query. Then order calls and get last one with limit.
SELECT *
FROM Customers,
Calls.CallId as LastCalledId
Calls.CallDate as LastCalledDate
Calls.CallId as NextCallId
LEFT JOIN
Calls ON (Customers.CustomerId = Calls.CustomerId AND Calls.Status = 1)
ORDER BY Calls.CallDate DESC
UNION
SELECT *
FROM Customers,
Calls.CallId as LastCalledId
Calls.CallId as NextCallId
Calls.CallDate as NextCallDate
LEFT JOIN
Calls ON (Customers.CustomerId = Calls.CustomerId AND Calls.Status = 0 AND CallDate > NOW())
ORDER BY Calls.CallDate DESC;

Answer 5

You can do this using different ways :
Select cu.CustomerId,LastCall.Callid,LastCall.calldate,NextCall.Callid,NextCall.calldate from Customers cu,
(select max(callid) Callid,max(calldate) calldate,CustomerId from Calls c where status = 1 group by CustomerId) LastCall,
(select max(callid) Callid,max(calldate) calldate,CustomerId from Calls c where status = 0 and calldate > sysdate group by CustomerId) NextCall
where cu.CustomerId = LastCall.CustomerId and cu.CustomerId = NextCall.CustomerId
order by 1
Or by replacing in your query :
Select (select max(callid) from Calls c where c.CustomerId = Cu.CustomerId and status = 1) as LastCalledId,
(select max(CallDate) from Calls c where c.callid = (select max(callid) from Calls c where c.CustomerId = Cu.CustomerId and status = 1)) as LastCalledDate,
(select max(callid) from Calls c where c.CustomerId = Cu.CustomerId and status = 0 and CallDate > sysdate ) as NextCallId,
(select max(CallDate) from Calls c where c.callid = (select max(callid) from Calls c where c.CustomerId = Cu.CustomerId and status = 0 and CallDate > sysdate )) as NextCallDate
From Customers Cu,Calls c ON Cu.CustomerId = c.CustomerId