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/* BEST TIME TO ASK QUESTIONS

The best time here is when the delay between a question and an accepted
answer is shortest.

On the graph, look for the value on the x-axis that
corresponds to the minimum value on y-axis.
That's the best time to ask questions as defined above.

As for Dec 2013, the smallest time-to-answer was for questions asked
on Saturday at 1pm GMT. The asker had to wait for only 78 minutes.

Axes:
- X: Hours, days of week, or both
    1.0 is Sunday, 12am GMT; 3.5 means Tuesday, 12pm GMT.
- Y: Time-to-answer. The average difference between the time when
    the question was created and when the accepted answer was created.

Parameters:
- All: Include all users or only one specified by UserId
    Values: 0 - show stats for one user, 1 - for all users
- Frequency: The scale of X-axis
    Values: 1 - hours, 2 - day of week, 3 - both
- MaxTimeDiff: The cut off value for time difference. All time-to-answer
    above this value will be excluded from the statistics.
    Default value: 1440 min (24 hours).
- UserId: Whose stats to include in calculations. Matters only when All = 0.
    Values: Your user ID or someone else's.
- YearsBack: How far to go back in getting statistics. Default is "1" (year)
    and data shows that the timerange doesn't matter much.
*/


DECLARE @All int = ##All:int?1##
DECLARE @Frequency int = ##Frequency:int?3##
DECLARE @MaxTimeDiff int = ##MaxTimeDiff:int?1440##
DECLARE @UsedId int = ##UserId:int##
DECLARE @YearsBack int = 1

;WITH tmp AS
(
  SELECT TimeDiff = DATEDIFF(minute, q.CreationDate, a.CreationDate),
         Period = CASE @Frequency
           WHEN 1 THEN DATEPART("hour", q.CreationDate)
           WHEN 2 THEN DATEPART("weekday", q.CreationDate)
           WHEN 3 THEN ROUND((CAST(DATEPART("weekday", q.CreationDate) AS numeric) +
             CAST(DATEPART("hour", q.CreationDate) AS numeric) / 24), 2) END
  FROM Posts q
    LEFT OUTER JOIN Posts a ON q.AcceptedAnswerId = a.Id
  WHERE q.AcceptedAnswerId > 0
    AND q.OwnerUserId = CASE WHEN @All = 1 THEN q.OwnerUserId ELSE @UsedId END
    AND q.CreationDate > DATEADD("year", -@YearsBack, CURRENT_TIMESTAMP)
  )
  SELECT Period,
  ROUND(AVG(CAST(TimeDiff AS FLOAT)), 2) AS [Average time-to-answer, minutes, UTC (GMT)]
FROM tmp
WHERE ABS(TimeDiff) < @MaxTimeDiff
GROUP BY Period
ORDER BY Period

fork query

edited dec 24 13

created dec 21 13 Anton.