Convert integer into datetime (dd:hh:mm:ss) - mysql

Question

SELECT AVG (closeTime - createTime)
FROM Deals
WHERE dealid = 123
The 'closeTime' and 'addTime' have a DATETIME ( YYYY-MM-DD HH:MI:SS ) format. The result is:
105030215.0000
Which function should I use to convert this value into a DATETIME?
addTime: 12/04/2016 13:06
closeTime: 12/05/2017 16:08
Result that I am looking for (which I calculated in Excel):
29:03:02:15 (DD:HH:MM:SS)

Answer 1

Subtracting DATETIMEs in MySQL does not appear to give the difference between them in seconds. With your two example dates, 2016-04-12 13:06 and 2016-05-12 16:08 (assuming the 2017 in your question is a typo), subtracting them returns 100030200 whereas the correct answer is 2602920. This is out by a factor of 38.4 and a bit.
The MySQL function to return the difference in seconds is TIMESTAMPDIFF and, indeed, SELECT TIMESTAMPDIFF(SECOND, '2016-04-12 13:06', '2016-05-12 16:08') returns the correct number of seconds.
Now all we need to do is convert it into your format. MySQL has a built-in function SEC_TO_TIME which sort of does this, but unfortunately it doesn't work for periods of more than 839 hours and it doesn't itemise the days separately. We can work around this by calculating the days separately from the rest of the calculation and using SEC_TO_TIME on the leftovers once the days have been subtracted from the difference.
SELECT CONCAT(
TIMESTAMPDIFF(DAY, '2016-04-12 13:06', '2016-05-12 16:08'), ':',
SEC_TO_TIME(TIMESTAMPDIFF(SECOND, '2016-04-12 13:06', '2016-05-12 16:08') % 86400));
-- 30:03:02:00 (DD:HH:MM:SS)
This appears to be the correct answer. Although your desired output was 29:03:02:15, there were 30 days in April, and no seconds in the inputs at all.
As you're using an aggregate function to determine the number of seconds, we won't be able to select the value in days separately from the value in seconds (otherwise we'd get the average number of days followed by part of the average number of seconds), so you'll have to rewrite this as
SELECT CONCAT(
FLOOR(AVG(TIMESTAMPDIFF(SECOND, createTime, closeTime)) / 86400), ':',
SEC_TO_TIME(AVG(TIMESTAMPDIFF(SECOND, createTime, closeTime)) % 86400))
FROM deals WHERE dealid = 123;
-- 30:03:02:00.0000
This now includes fractions of a second because the average difference might not be a round number of seconds. To exclude them, use FLOOR or ROUND.
SELECT CONCAT(
FLOOR(AVG(TIMESTAMPDIFF(SECOND, createTime, closeTime)) / 86400), ':',
SEC_TO_TIME(ROUND(AVG(TIMESTAMPDIFF(SECOND, createTime, closeTime))) % 86400))
FROM deals WHERE dealid = 123;