T-SQL Join with "max" filter - sql

Question

I'm using SQL Server 2014.
I'd like the following to give me no duplicate phone ID's or numbers:
WITH Phones as
(
SELECT * FROM (VALUES
(1,'602 600 8000'),
(2,'602 600 8001'),
(3,'602 600 8002')
) AS Vict_t (Id,Number)
), InvoicePhones as
(
SELECT * FROM (VALUES
(10, 1, 100, 'Alpha'),
(11, 1, 101, 'Bravo'),
(12, 1, 102, 'Charlie'),
(13, 2, 103, 'Alpha'),
(14, 2, 104, 'Bravo'),
(15, 2, 105, 'Charlie'),
(16, 3, 106, 'Alpha'),
(17, 3, 107, 'Bravo'),
(18, 3, 108, 'Charlie')
) as ip_t (Id,PhoneId,VoiceId, Name)
), Voices as
(
SELECT * FROM (VALUES
(100, '201701'),
(101, '201702'),
(102, '201703'),
(103, '201704'),
(104, '201705'),
(105, '201706'),
(106, '201708'),
(107, '201709'),
(108, '201710')
) AS Voices_t (Id,BillingCycle)
)
SELECT P.Id PhoneId, P.Number, IP.Name
FROM Phones P
LEFT JOIN InvoicePhones IP on IP.PhoneId = P.Id and IP.VoiceId =
(
select TOP 1 id
from Voices V
where V.Id = IP.VoiceId
order by V.BillingCycle desc
)
I cannot understand why the sub-select is not eliminating the duplicates.
What I'm receiving is this:
1 602 600 8000 Alpha
1 602 600 8000 Bravo
1 602 600 8000 Charlie
2 602 600 8001 Alpha
2 602 600 8001 Bravo
2 602 600 8001 Charlie
3 602 600 8002 Alpha
3 602 600 8002 Bravo
3 602 600 8002 Charlie
What I'm expecting is this:
1 602 600 8000 Charlie
2 602 600 8001 Charlie
3 602 600 8002 Charlie
This example uses simple integer ID's, but the real tables I'm working with are using uniqueidentifier. Thus the answer I need must take that into account.
I tried both versions of this accepted answer, but it doesn't work for me.
What am I missing?
Update
In addition to the answer I chose, I realized another way to solve this problem is as follows:
SELECT P.Id PhoneId, P.Number, IP.Name
FROM Phones P
LEFT JOIN InvoicePhones IP on IP.PhoneId = P.Id and IP.VoiceId =
(
select TOP 1 V.Id
from Voices V
INNER JOIN InvoicePhones IPS ON IPS.VoiceId = V.Id
WHERE P.Id = IPS.PhoneId
order by V.BillingCycle desc
)
I'm curious if they can also be solved with an OUTER APPLY, as mentioned in this other SO post

Answer 1

Looks like you need use ROW_NUMBER() to get the latest ID, but the final logic or the need for the third table isnt clear.
SQL DEMO
), filter as (
SELECT P.Id PhoneId, P.Number, IP.Name, IP.VoiceId,
ROW_NUMBER() OVER (PARTITION BY P.Id ORDER BY VoiceID DESC) as rn
FROM Phones P
LEFT JOIN InvoicePhones IP on IP.PhoneId = P.Id
)
SELECT *
FROM filter
WHERE rn = 1
OUTPUT
To include the third table:
SQL DEMO
), filter as (
SELECT P.Id PhoneId, P.Number, IP.Name, IP.VoiceId, V.*,
ROW_NUMBER() OVER (PARTITION BY P.Id ORDER BY BillingCycle DESC) as rn
FROM Phones P
LEFT JOIN InvoicePhones IP on IP.PhoneId = P.Id
LEFT JOIN Voices V on V.Id = IP.VoiceId
)
SELECT *
FROM filter
WHERE rn = 1
OUTPUT

Answer 2

I'm not sure what you want. But you have this condition:
IP.VoiceId = (select TOP 1 id
from Voices V
where V.Id = IP.VoiceId
order by V.BillingCycle desc
)
The correlation clause is V.id = IP.VoiceId. The equality comparison is -- essentially -- IP.VoiceId = V.id. They are the same. As long as there is at least one matching record in Voices, then the IP record passes the test. With your data, all IP records pass the test.
I'm not sure what you are really trying to accomplish. If you want only one row per phone, then I would be thinking EXISTS or IN.
The simplest way to get the results you want is:
select p.*
from phones p;
I suspect that you want more sophisticated logic, however.

Answer 3

;WITH Phones as
(
SELECT * FROM (VALUES
(1,'602 600 8000'),
(2,'602 600 8001'),
(3,'602 600 8002')
) AS Vict_t (Id,Number)
), InvoicePhones as
(
SELECT * FROM (VALUES
(10, 1, 100, 'Alpha'),
(11, 1, 101, 'Bravo'),
(12, 1, 102, 'Charlie'),
(13, 2, 103, 'Alpha'),
(14, 2, 104, 'Bravo'),
(15, 2, 105, 'Charlie'),
(16, 3, 106, 'Alpha'),
(17, 3, 107, 'Bravo'),
(18, 3, 108, 'Charlie')
) as ip_t (Id,PhoneId,VoiceId, Name)
), Voices as
(
SELECT * FROM (VALUES
(100, '201701'),
(101, '201702'),
(102, '201703'),
(103, '201704'),
(104, '201705'),
(105, '201706'),
(106, '201708'),
(107, '201709'),
(108, '201710')
) AS Voices_t (Id,BillingCycle)
)
,Expected
AS
(
SELECT P.Id PhoneId, P.Number, IP.Name
FROM Phones P
LEFT JOIN InvoicePhones IP on IP.PhoneId = P.Id and IP.VoiceId =
(
SELECT TOP 1 id
FROM Voices V
WHERE V.Id = IP.VoiceId
ORDER BY V.BillingCycle desc
)
)
SELECT PhoneId,Number,Name From
(
SELECT *,ROW_NUMBER()OVER(PARTITION BY Phoneid,Number ORDER BY Phoneid)AS Seq
FROM Expected
)DT
WHERE DT.Seq=3
OutPut
PhoneId Number Name
------------------------------
1 602 600 8000 Charlie
2 602 600 8001 Charlie
3 602 600 8002 Charlie