Question

I have a data entry form that anybody must fill up 3 forms. I log the entry time for form 1, form 2, form 3. Now I want to know what is the average of time to fill up the forms for all people. How can I do that?

Answer 1

100% guesswork based on extremely vague requirements.

DECLARE @x TABLE
(
    UserID    INT,
    FormID    TINYINT,
    StartTime DATETIME,
    EndTime   DATETIME
);

INSERT @x VALUES

-- a user who has completed all three forms
    (1,1,'20110820 04:25:01','20110820 04:33:07'),
    (1,2,'20110820 04:34:05','20110820 04:38:33'),
    (1,3,'20110820 04:39:02','20110820 04:47:55'),

-- a user who has completed two forms
    (2,1,'20110820 04:25:54','20110820 04:29:32'),
    (2,2,'20110820 04:30:55','20110820 04:34:27'),

-- the same user who has completed 1.5 forms
    (2,1,'20110820 04:35:23','20110820 04:37:15'),
    (2,2,'20110820 04:38:34',NULL),

-- the same user who has completed all three forms
    (2,1,'20110820 04:45:12','20110820 04:49:07'),
    (2,2,'20110820 04:50:26','20110820 04:55:31'),
    (2,3,'20110820 04:56:41','20110820 05:01:23'),

-- a slow user who has completed all three forms
    (3,1,'20110820 05:25:04','20110820 05:43:07'),
    (3,2,'20110820 05:44:09','20110820 05:55:21'),
    (3,3,'20110820 05:59:41','20110820 06:24:23');

Here are some typical aggregations that I’m guessing might hit the one you’re looking for:

SELECT -- avg by form regardless of user
    FormID, 
    completed_forms = COUNT(*), 
    average = AVG(DATEDIFF(SECOND, StartTime, EndTime))
FROM @x GROUP BY FormID;

SELECT -- avg by form and user
    UserID,
    FormID, 
    completed_forms = COUNT(*),
    [seconds] = AVG(DATEDIFF(SECOND, StartTime, EndTime))
FROM @x GROUP BY UserID, FormID;

SELECT -- avg by user regardless of form
    UserID,
    completed_forms = COUNT(*),
    [seconds] = AVG(DATEDIFF(SECOND, StartTime, EndTime))
FROM @x GROUP BY UserID;

-- if you want hh:mm:ss format and the form never takes > 24 hours to complete,
-- you can do this kind of thing to any of the above queries:

;WITH x(FormID, completed_forms, average) AS
(
    SELECT
        FormID,
        COUNT(*),
        AVG(DATEDIFF(SECOND, StartTime, EndTime))
    FROM @x GROUP BY FormID
)
SELECT 
    FormID, 
    completed_forms,
    [hh:mm:ss] = CONVERT(CHAR(8), (CONVERT(TIME(0), DATEADD(SECOND, average, '19000101'))))
FROM x;