SQL Showing Less information depending on date - sql

Question

I have this code, what It returns is a list of some clients, but it lists too many. This is because it lists several of the same thing just with diffrent dates. I only want to show the latest date and none of the other ones. I tried to do a group by Client_Code but it didn't work, it just through up not an aggregate function or something similar (can get if needed). What I have been asked to get is all of our clients, with all the details listed. in the 'as' part and they all pull through properly. If I take out:
I.DATE_LAST_POSTED as 'Last Posted',
I.DATE_LAST_BILLED as 'Last Billed'
It shows up okay, but I need the last billed date only to appear. But putting these lines in shows the client several times listing all the diffrent bill dates. And I think that is because it is pulling across the diffrent Matters in the Matter_Master Table. Essentially, I would like to only show the Client Information on the highest Matter with there last billed date.
Please let me know if this needs clarification, im trying to explain best I can....
SELECT DISTINCT
A.DIWOR as 'ID',
B.Client_alpha_Name as 'Client Name',
A.ClientCODE as 'Client Code',
B.Client_address as 'Client Address',
D.COMM_NO AS 'Contact',
E.Contact_full_name as 'Possible Key Contact',
G.LOBSICDESC as 'LOBSIC Code',
H.EARNERNAME as 'Client Care Parnter',
A.CLIENTCODE + '/' + LTRIM(STR(A.LAST_MATTER_NUM)) as 'Last Matter Code',
I.DATE_LAST_POSTED as 'Last Posted',
I.DATE_LAST_BILLED as 'Last Billed'
FROM CLIENT_MASTER A
JOIN CLIENT_INFO B
ON A.CLIENTCODE=B.CLIENT_CODE
JOIN MATTER_MASTER C
ON A.DIWOR=C.CLIENTDIWOR
JOIN COMMINFO D
ON A.DIWOR=D.DIWOR
JOIN CONTACT E
ON A.CLIENTCODE=E.CLIENTCODE
JOIN VW_CONTACT F
ON E.NAME_DIWOR=F.NAME_DIWOR
JOIN LOBSIC_CODES G
ON A.LOBSICDIWOR=G.DIWOR
JOIN STAFF H
ON A.CLIENTCAREPARTNER=H.DIWOR
JOIN MATTER I
ON C.DIWOR=I.MATTER_DIWOR
WHERE F.COMPANY_FLAG='Y'
AND C.MATTER_MANAGER NOT IN ('78','466','2','104','408','73','51','561','504','101','13','534','16','461','531','144','57','365','83','107','502','514','451')
AND I.DATE_LAST_BILLED > 0
GROUP BY A.ClientCODE
ORDER BY A.DIWOR

Answer 1

Your problem is that you aren't using enough aggregate functions. Which is probably why you're using both the DISTINCT clause and the GROUP BY clause (the recommendation is to use GROUP BY, and not DISTINCT).
So... remove DISTINCT, add the necessary (unique, more or less) list of columns to the GROUP BY clause, and wrap the rest in aggregate functions, constants, or subselects. In the specific case of wanting the largest date, wrap it in a MAX() function.

Answer 2

If I understood right:
--=======================
-- sample data - simplifed output of your query
--=======================
declare #t table
(
ClientCode int,
ClientAddress varchar(50),
DateLastBilled datetime
-- the rest of fields is skipped
)
insert into #t values (1, 'address1', '2011-01-01')
insert into #t values (1, 'address1', '2011-01-02')
insert into #t values (1, 'address1', '2011-01-03')
insert into #t values (1, 'address1', '2011-01-04')
insert into #t values (2, 'address2', '2011-01-07')
insert into #t values (2, 'address2', '2011-01-08')
insert into #t values (2, 'address2', '2011-01-09')
insert into #t values (2, 'address2', '2011-01-10')
--=======================
-- solution
--=======================
select distinct
ClientCode,
ClientAddress,
DateLastBilled
from
(
select
ClientCode,
ClientAddress,
DateLastBilled,
-- list of remaining fields
MaxDateLastBilled = max(DateLastBilled) over(partition by ClientCode)
from
(
-- here should be your query
select * from #t
) t
) t
where MaxDateLastBilled = DateLastBilled