sql get max of multiple results - sql

Question

In SQL server 2008 R2, how do you get the MAX result if you have two rows that have the same value? I have a table that I use to store the data about the number of times a client is seen at a location.
create table #templocation
(
ClientID Int,
Location Varchar(100),
LocationCount Int,
MaxCount Int
)
I only fill the first three columns with an insert statement then I get the max for each client like this:
update t
set t.MaxCount = t2.locationcount
from #templocation t
join (select tl.ClientID, MAX(tl.LocationCount) as 'locationcount'
from #templocation tl
group by tl.ClientID) t2
on t2.ClientID = t.ClientID
update t
set t.PrimaryLocation = tl.Location
from #temp t
join #templocation tl
on t.ClientId = tl.ClientID
where tl.LocationCount = tl.MaxCount
I then join this to the main table to get the final results. My problem is if a client is has two or more max counts. Then it wants to display all of the max locations like this:
ClientId Location LocationCount
12502 Main St. 4
12502 Lake Ave 4
12502 Tracy Rd 2
The results I get are:
ClientId ClientName Location
12502 John Smith Main St.
12502 John Smith Lake Ave
I only want the first or top one displayed though preferably by alphabetical order.

Answer 1

I do things like this through a couple of CTEs. One will give us the max(locationcount) for each client, and one just adds a row_number() for every clientid so we can pick the "first" location".
SQL Fiddle
It's a bit of a hack, but it works.
;with maxrows as
(select
ClientID as ClientID,
max(LocationCount) as MaxValue
--row_number() OVER (partition by ClientID order by ClientID)
from
table1
group by ClientID)
,
rowcounts as
(
select
t1.ClientID,
t1.Location,
row_number() over (PARTITION BY t1.ClientID order by t1.Location) as RowNum
from
table1 t1
)
select
t2.ClientID,
t2.Location
from
maxrows t1
inner join rowcounts t2
on t1.ClientID = t2.ClientID
and t2.rownum = 1

Answer 2

From how I understood the issue, you could use MAX() OVER () to achieve what you want like this:
WITH maxvalues AS (
SELECT
ClientId,
Location,
LocationCount,
MaxCount = MAX(LocationCount) OVER (PARTITION BY ClientId)
FROM atable
)
SELECT
ClientId,
Location
FROM maxvalues
WHERE LocationCount = MaxCount
;
Join maxvalues to whatever table holds the client names to include those into the output too.
Learn more about the OVER clause in this manual:
OVER clause (Transact-SQL)