selecting the max values based on a count - sql

Question

How can i retrieve the max of each ValueCount based on the firmid. I need the data to be output like so.
My code is below
SELECT
F.FirmID,
F.Name,
DL.ValueId,
DL.ValueName,
count(DL.ValueName) AS ValueCount
FROM
dbo.Jobs AS J
INNER JOIN DimensionValues AS DV ON
DV.CrossRef = J.JobId
INNER JOIN dbo.DimensionLists AS DL ON
DV.ValueId = DL.ValueId
INNER JOIN Firms AS F ON
F.FirmId = J.ClientFirmId
WHERE
DL.DimensionId = 4
GROUP BY
F.FirmID,
F.Name,
DL.ValueName,
DL.ValueId
this produces something like
firmid | value | count
1 1 5
1 2 10
2 3 1
2 1 6
i need to return back the records with 10 and 6.

Answer 1

EDIT : SQL 2005 answer deleted.
Then you could push your results into a temporary table (or table variable) and do something like this...
SELECT
*
FROM
TempTable
WHERE
ValueCount = (SELECT MAX(ValueCount) FROM TempTable AS Lookup WHERE FirmID = TempTable.FirmID)
Or...
SELECT
*
FROM
TempTable
INNER JOIN
(SELECT FirmID, MAX(ValueCount) AS ValueCount FROM TempTable GROUP BY FirmID) AS lookup
ON lookup.FirmID = TempTable.FirmID
AND lookup.ValueCount = TempTable.ValueCount
These will give multiple records if any ValueCount is tied with another for the same FirmID. As such, you could try this...
SELECT
*
FROM
TempTable
WHERE
value = (
SELECT TOP 1
value
FROM
TempTable as lookup
WHERE
FirmID = TempTable.FirmID
ORDER BY
ValueCount DESC
)

Answer 2

For this problem you need to produce the result set of the query in order to determine the Max ValueCount, then you need to do the query again to pull just the records with Max ValueCount. You can do this many way, like repeating the main query as subqueries, and in SQL Server 2005/2008 by using a CTE. I think using the subqueries gets a little messy and would prefer the CTE, but for SQL Server 2000 you don't have that as an option. So, I've used a temp table instead of a CTE. I run it once to get the MaxValueCount and save that into a temp table, then run the query again and join against the temp table to get just the record with MaxValueCount.
create table #tempMax
(
FirmID int,
MaxValueCount int
)
insert #tempMax
SELECT t.FirmID, MAX(t.ValueCount) AS MaxValueCount
FROM (
SELECT F.FirmID, F.Name, DL.ValueId, DL.ValueName
, count(DL.ValueName) AS ValueCount
FROM dbo.Jobs AS J
INNER JOIN DimensionValues AS DV ON DV.CrossRef = J.JobId
INNER JOIN dbo.DimensionLists AS DL ON DV.ValueId = DL.ValueId
INNER JOIN Firms AS F ON F.FirmId = J.ClientFirmId
WHERE DL.DimensionId = 4
GROUP BY F.FirmID, F.Name, DL.ValueName, DL.ValueId) t
SELECT t.FirmID, t.Name, t.ValueID, t.ValueName, t.ValueCount
FROM (
SELECT F.FirmID, F.Name, DL.ValueId, DL.ValueName
, count(DL.ValueName) AS ValueCount
FROM dbo.Jobs AS J
INNER JOIN DimensionValues AS DV ON DV.CrossRef = J.JobId
INNER JOIN dbo.DimensionLists AS DL ON DV.ValueId = DL.ValueId
INNER JOIN Firms AS F ON F.FirmId = J.ClientFirmId
WHERE DL.DimensionId = 4
GROUP BY F.FirmID, F.Name, DL.ValueName, DL.ValueId) t
INNER JOIN #tempMax m ON t.FirmID = m.FirmID and t.ValueCount = m.MaxValueCount
DROP TABLE #tempMax

Answer 3

You should be able to use a derived table for this:
SELECT F.FirmID,
F.Name,
DL.ValueId,
DL.ValueName,
T.ValueCount
FROM Jobs J
INNER JOIN DimensionValues DV
ON DV.Crossref = J.JobID
INNER JOIN DimensionList DL
ON DV.ValueID = DL.ValueID
INNER JOIN Firms F
ON F.FirmID = J.ClientFirmID
--derived table
INNER JOIN (SELECT FirmID, MAX(ValueName) ValueCount FROM DimensionList GROUP BY FirmID) T
ON T.FirmID = F.FirmID
WHERE DL.DimensionId = 4

Answer 4

TBL1 and TBL2 is your query:
SELECT *
FROM TBL1
WHERE
TBL1.ValueCount = (SELECT MAX(TBL2.ValueCount) FROM TBL2 WHERE TBL2.FIRMID = TBL1.FIRMID)