how to calculate percent of total within group by statement?

Question

I have a table with 1 record per sale per salesperson per day

NAME  DATE
joe   1-1-13
joe   1-1-13
joe   1-1-13
dave  1-1-13
joe   1-2-13

I

Answer 1

Use a nested query to get the daily total:

BEGIN

    create table #sales (name varchar(10), salesdate date )

    insert into #sales (name, salesdate) values 
        ('joe', '01-01-2013'), 
        ('joe', '01-01-2013'), 
        ('joe', '01-01-2013'), 
        ('dave', '01-01-2013'),  
        ('joe', '01-02-2013'),
        ('dave', '01-02-2013')

    SELECT name, salesdate, COUNT(*) AS personDailyTotal, MAX(dailyTotal) AS dailyTotal, 
        (COUNT(*) * 100.0) / MAX(dailyTotal) AS [Percent]
    FROM #sales
    INNER JOIN (
        SELECT salesdate as [day], COUNT(*) as dailyTotal 
        FROM #sales 
        GROUP BY salesdate
    ) AS [Total] ON salesdate = [day]
    GROUP BY name, salesdate

END