I have a data base with several payments for each participant.
Each payment has participant number and date-of-payment.
I'd like to easily and QUICKLY calculate the Median number of days between payments for each participant.
I found a method using a sub-query, but, it ran for over 12 hours on only about 30,000 rows.
I'd like to be able to run it on a half-million rows in less than an hour.