SQL statement using WHERE from a GROUP or RANK

问题

I have a sales snapshot with about 35,000 rows. Let's call the columns:

Sales Rep | Account ID | Total Contract Value | Date

I need to group everything by Sales Rep and then from there, select that Sales Rep's top 35 accounts based off of Total Contract Value where the Total Contract Value is >= $10,000 for the Month (Date) of January 2013.

So for example, say John Doe had 294 accounts in this table from January, I only want to see his top 35 accounts >= $10,000 , same for Jane Doe, etc. etc. It's very important that the query be as efficient in it's resource usage as possible.

Thoughts?

回答1:

For this, you want to use a function called row_number():

select ss.*
from (select ss.*, row_number() over (partition by salesrep order by ContractValue desc) as seqnum
      from snapshot ss
      where TotalContractValue >= 10000 and date between '2013-01-01' and '2013-01-31'
     ) ss
where seqnum <= 35

You don't specify the database you are using. In databases that don't have row_number(), there are alternatives that are less efficient.

回答2:

The answer is already in your title, partition by SalesRep and AccountID and Rank by Total Contact Value.

A SQL Server solution will look like:

DECLARE @minimumValue decimal(20,2) = 10000
DECLARE @numberOfAccounts int = 35
DECLARE @from datetime = '1/1/2013'
DECLARE @till datetime = DATEADD(MONTH, 1, @from)

SELECT 
  [sub].[Sales Rep],
  [sub].[Rank],
  [sub].[Account ID],
  [sub].[Total Contract Value]
FROM
(
  SELECT
    [Sales Rep],
    [Account ID],
    [Total Contract Value],
    DENSE_RANK() OVER (PARTITION BY [Sales Rep] ORDER BY [Total Contract Value] DESC) AS [Rank]
  FROM [Sales]
  WHERE
    [Total Contract Value] >= @minimumValue
    AND [Date] > @from
    AND [Date] < @till
) AS [sub]
WHERE [sub].[Rank] <= @numberOfAccounts
ORDER BY 
  [Sales Rep] ASC,
  [Rank] ASC

Here is a (simple) Sql Fiddle.

来源：https://stackoverflow.com/questions/14654855/sql-statement-using-where-from-a-group-or-rank