Question

It returns all rows sorted by CountOfRecords DESC. I’d like to have just seven rows here, showing the highest value ever for the specified day. So each day of the week should occur once and only once. Is this possible without a lot of pain?

SELECT 
    Count(*) As CountOfRecords, 
    CAST(FLOOR(CAST([visit].[datetimeentered] AS float)) AS smalldatetime) AS DateEntered, 
    DatePart(dw, visit.datetimeentered) As DayOfTheWeek
FROM visit
INNER JOIN useragent ON useragent.useragentid = visit.useragentid
WHERE useragent.isbot = 0
GROUP BY CAST(FLOOR(CAST([visit].[datetimeentered] AS float)) AS smalldatetime), 
    DatePart(dw, visit.datetimeentered)
ORDER BY CountOfRecords DESC

Edit1:
I think both answers are getting at the same thing. I’ve accepted the one that was posted first. I’m also going to mention that it worked right off the bat while the other did not. I’m getting the following errors when I run marc_s’s query:

Msg 207, Level 16, State 1, Line 29
Invalid column name 'RowNum'.
Msg 207, Level 16, State 1, Line 25
Invalid column name 'CountOfRecords'.
Msg 207, Level 16, State 1, Line 26
Invalid column name 'DateEntered'.
Msg 207, Level 16, State 1, Line 27
Invalid column name 'DayOfTheWeek'.

Special thanks to marc_s for pointing out a simple way to get the only the date portion from a datetime.

Answer 1

Based on your query:

WITH groupedByDay AS (
  SELECT 
    Count(*) As CountOfRecords, 
    CAST(FLOOR(CAST([visit].[datetimeentered] AS float)) AS smalldatetime) AS DateEntered
  FROM visit
  INNER JOIN useragent ON useragent.useragentid = visit.useragentid
  WHERE useragent.isbot = 0
  GROUP BY CAST(FLOOR(CAST([visit].[datetimeentered] AS float)) AS smalldatetime)
),
ranked AS (
  SELECT
    CountOfRecords,
    DateEntered,
    DOW = DATENAME(dw, DateEntered),
    rank = ROW_NUMBER() OVER (PARTITION BY DatePart(dw, DateEntered)
                              ORDER BY CountOfRecords DESC)
  FROM groupedByDay
)
SELECT
  CountOfRecords,
  DateEntered,
  DOW
FROM ranked
WHERE rank = 1
ORDER BY CountOfRecords DESC

This will return one row for each day of week represented in the table. If there may be duplicates by CountOfRecords among the maximum values and you want to return them all, use RANK() instead of ROW_NUMBER().