Forum Discussion
DATEDIFF between duplicate IDs
Hi all,
Wondering if anyone could help me work out how to approach the following challenge:
I have a table with millions of IDs in one columns, and dates of when they were sold in another.
In the event that an ID is repeated, it means the product has been resold and I need to calculate the average datediff between those two dates for the repeated IDs.
Would the best approach be to create another table by performing a Group By on the IDs? If so how would I then use the datediff to only calculate between the two dates relating to the repeated IDs?
Many thanks for any direction on this one!
Matt
So... we take the max(date sold) minus min(date sold) giving us the total # of days between sales, then divide by the number of sales (minus 1)... and that gives the average number of days between sales? I think?
Jan 1, 2017
Jan 9, 2017
... 8 days between sales -- Jan 9 - Jan 8 / (2 sales - 1) = 8
Jan 1, 2017
Jan 2, 2017
Jan 9, 2017
... still 8 days, but now with another sale, we get average of 4 days. The exact date off the "middle" sale doesn't matter, at least in my head!? Currently Jan2-Jan1=1, Jan9-Jan2=7, (7+1)/2=4 ?
Avg Days Between Sale := DIVIDE(MAX(MyTable[SaleDate]) - MIN(MyTable[SaleDate]), COUNTROWS(MyTable) - 1)Maybe?! :)
Hi again,
Qucik update, it turns out that my technical indications were incorrect and the sales are not going to coming through this way.
However, intrigued by the suggestion I've had a quick look through but can't seem to get it to work:
ID Date Sold Time taken to sell 1 01/01/2017 0 1 03/01/2017 2 3 05/01/2017 0 Average Days to Sell 3 10/01/2017 5 3,5 Jan10-Jan1 / 2 sales = 5? Jan10-Jan1 / (2-1) sales = 10? Many thanks for your help anyway.
Matt
6 Replies
So... we take the max(date sold) minus min(date sold) giving us the total # of days between sales, then divide by the number of sales (minus 1)... and that gives the average number of days between sales? I think?
Jan 1, 2017
Jan 9, 2017
... 8 days between sales -- Jan 9 - Jan 8 / (2 sales - 1) = 8
Jan 1, 2017
Jan 2, 2017
Jan 9, 2017
... still 8 days, but now with another sale, we get average of 4 days. The exact date off the "middle" sale doesn't matter, at least in my head!? Currently Jan2-Jan1=1, Jan9-Jan2=7, (7+1)/2=4 ?
Avg Days Between Sale := DIVIDE(MAX(MyTable[SaleDate]) - MIN(MyTable[SaleDate]), COUNTROWS(MyTable) - 1)Maybe?! :)