Question

I have a table that tracks emails sent from applications on my server. I would like to write a query that shows how many emails were sent by each application in a certain time period. Here is the table:

---------------------------------------------------------- 
|  emailID  |          SentDT          | ApplicationName | 
---------------------------------------------------------- 
|    1      |  2011-08-04 14:43:31.080 |    Term Form    | 
---------------------------------------------------------- 
|    2      |  2011-08-04 13:59:46.062 |    Term Form    |
---------------------------------------------------------- 
|    3      |  2011-08-03 10:38:15.015 |  Request Form   |
---------------------------------------------------------- 
|    4      |  2011-08-03 05:52:29.005 |    Term Form    |
---------------------------------------------------------- 
|    5      |  2011-08-01 19:58:31.094 | Recruiting Form |  
----------------------------------------------------------

I would like to see number of emails sent Today, Last 24 hours, Last 7 days, This Month, Last Month, All time.

I know how to do each of these queries by themselves, but I have no clue how to do it in one trip to the database.

For example:

-------------------------------------------------------------- 
|  ApplicationName |  Today | Last24 | Last7days | ThisMonth |
-------------------------------------------------------------- 
|    Term Form     |    2   |   5    |   10      |    19     |
--------------------------------------------------------------
|   Request Form   |    9   |   18   |   36      |    75     |
--------------------------------------------------------------
|  Recruiting Form |    15  |   35   |   100     |    250    |
--------------------------------------------------------------

I tried using a nested select for each subset of times, but I can’t use a group by in the nested select. My query that doesn’t produce results:

select COUNT(emailID), ApplicationName, (select COUNT(emailID) from emaillog where SentDT > '08/02/2011') as TwoDaysAgo
 from emaillog
 group by ApplicationName
 order by ApplicationName

Answer 1

I think it’s much easier to do all the date calculations up front, then you can refer to local variables with logical names instead of embedding all the datediff/case etc. calculations in the query logic.

Made a couple of assumptions here. (1) that no data in EmailLog is in the future (2) that by “Last 7 days” you mean today and the full 6 days preceding. I’ve also included a grand total – even though it’s not listed in your desired output, it seems you were trying to get it with the COUNT() outside the subquery.

DECLARE @now SMALLDATETIME = SYSDATETIME();

DECLARE @today DATE = @now, 
        @24hrsago SMALLDATETIME = DATEADD(DAY, -1, @now);

DECLARE @7daysago DATE = DATEADD(DAY, -6, @today),
        @ThisMonth DATE = DATEADD(DAY, 1-DATEPART(DAY, @today), @today);

--SELECT @now, @today, @24hrsago, @7daysago, @ThisMonth;

WITH d AS
(
    SELECT ApplicationName, c = COUNT(*)
    FROM EmailLog
    GROUP BY ApplicationName
),
g AS
(
    SELECT
        ApplicationName,
        [Today]     = SUM(CASE WHEN SentDt >= @today     THEN 1 ELSE 0 END),
        [Last24]    = SUM(CASE WHEN SentDt >= @24hrsago  THEN 1 ELSE 0 END),
        [Last7Days] = SUM(CASE WHEN SentDt >= @7daysago  THEN 1 ELSE 0 END),
        [ThisMonth] = SUM(CASE WHEN SentDt >= @ThisMonth THEN 1 ELSE 0 END)
    FROM EmailLog
    GROUP BY ApplicationName
)
SELECT d.ApplicationName,
    Total = d.c,
    [Today] = COALESCE(g.[Today], 0),
    [Last24] = COALESCE(g.[Last24], 0),
    [Last7days] = COALESCE(g.Last7days, 0),
    [ThisMonth] = COALESCE(g.ThisMonth, 0)
FROM d LEFT OUTER JOIN g
ON d.ApplicationName = g.ApplicationName;

EDIT

If my assumption was wrong and you don’t need the total count by application name, the query becomes much simpler:

DECLARE @now SMALLDATETIME = SYSDATETIME();

DECLARE @today DATE = @now, 
        @24hrsago SMALLDATETIME = DATEADD(DAY, -1, @now);

DECLARE @7daysago DATE = DATEADD(DAY, -6, @today),
        @ThisMonth DATE = DATEADD(DAY, 1-DATEPART(DAY, @today), @today);

SELECT ApplicationName,
    [Today]     = SUM(CASE WHEN SentDt >= @today     THEN 1 ELSE 0 END),
    [Last24]    = SUM(CASE WHEN SentDt >= @24hrsago  THEN 1 ELSE 0 END),
    [Last7Days] = SUM(CASE WHEN SentDt >= @7daysago  THEN 1 ELSE 0 END),
    [ThisMonth] = SUM(CASE WHEN SentDt >= @ThisMonth THEN 1 ELSE 0 END)
FROM EmailLog
GROUP BY ApplicationName;

Ordering optional of course.