SQL Server: aggregate to single result - sql

Question

I have this query
SELECT Client.ClientNo,
Client.ContactName,
Deal.Currency,
MAX(Deal.DealDate)
FROM Deal
JOIN Client ON Deal.ClientNo = Client.ClientNo
GROUP BY Client.ClientNo, Client.ContactName, Deal.Currency;
which gives me a result
1 John Smith EUR 2014-10-07
1 John Smith GBP 2014-11-12
2 Jane Doe GBP 2014-09-17
2 Jane Doe USD 2014-12-23
1 John Smith USD 2013-11-13
2 Jane Doe EUR 2012-09-06
Problem is, I need an aggregated result with the latest date per client, like this:
1 John Smith GBP 2014-11-12
2 Jane Doe USD 2014-12-23
How can I change my query to achieve this?
UPDATE Thanks to jarlh for the answer, however I have missed something - if there is a duplicate row - it will remain in the result, looking like this:
1 John Smith GBP 2014-11-12
1 John Smith GBP 2014-11-12
2 Jane Doe USD 2014-12-23
Any way to make that work?

Answer 1

You could do something like this:
Test data:
DECLARE #Deal TABLE(ClientNo INT,Currency VARCHAR(10),DealDate DATETIME)
DECLARE #Client TABLE(ClientNo INT,ContactName VARCHAR(100))
INSERT INTO #Deal
VALUES (1,'EUR','2014-10-07'),(1,'GBP','2014-11-12'),(2,'GBP','2014-09-17'),
(2,'USD','2014-12-23'),(1,'USD','2013-11-13'),(2,'EUR','2012-09-06')
INSERT INTO #Client
VALUES (1,'John Smith'),(2,'Jane Doe')
Query:
;WITH latestDeals
AS
(
SELECT
ROW_NUMBER() OVER(PARTITION BY ClientNo ORDER BY DealDate DESC) AS RowNbr,
Deal.*
FROM
#Deal AS Deal
)
SELECT
client.ClientNo,
client.ContactName,
latestDeals.Currency,
latestDeals.DealDate
FROM
#Client AS client
JOIN latestDeals
ON client.ClientNo=latestDeals.ClientNo
AND latestDeals.RowNbr=1
Update:
If you want to use conventional query. You could do something like this:
SELECT
client.ClientNo,
client.ContactName,
Latestdeal.maxDealDate as DealDate,
deal.Currency
FROM
#Client AS client
JOIN
(
SELECT
MAX(Deal.DealDate) AS maxDealDate,
Deal.ClientNo
FROM
#Deal AS Deal
GROUP BY
Deal.ClientNo
) AS Latestdeal
ON client.ClientNo=Latestdeal.ClientNo
JOIN #Deal as deal
ON client.ClientNo=deal.ClientNo
AND deal.DealDate=Latestdeal.maxDealDate
This will result in the same output
Result:
1 John Smith GBP 2014-11-12 00:00:00.000
2 Jane Doe USD 2014-12-23 00:00:00.000

Answer 2

Untested, but should work. Will return several rows for a clieant if the client has two (or more) deals the same, latest day.
SELECT Client.ClientNo,
Client.ContactName,
Deal.Currency,
Deal.DealDate
FROM Deal
JOIN Client ON Deal.ClientNo = Client.ClientNo
WHERE Deal.DealDate = (select max(DealDate) from Deal
where ClientNo = Client.ClientNo)

Answer 3

Try this,
Test Data:
CREATE TABLE #YourTable
(
CLIENT_NO INT,
CONTACT_NAME VARCHAR(20),
CURRENCY VARCHAR(10),
[DEAL_DATE] DATE
)
INSERT INTO #YourTable VALUES
(1,'John Smith','EUR','2014-10-07'),
(1,'John Smith','GBP','2014-11-12'),
(2,'Jane Doe','GBP','2014-09-17'),
(2,'Jane Doe','USD','2014-12-23'),
(1,'John Smith','USD','2013-11-13'),
(2,'Jane Doe','EUR','2012-09-06')
Query:
SELECT CLIENT_NO,CONTACT_NAME,CURRENCY,[DEAL_DATE]
FROM (SELECT *,
Row_Number()
OVER (
PARTITION BY CLIENT_NO
ORDER BY [DEAL_DATE] DESC) AS RN
FROM #YourTable)A
WHERE RN = 1