How to calculate the average time spent in the network?

Question

PHP

You need to find the total average time spent on the network and time per day. Let's say I have a table `active` with a large amount of data and it has two columns `login` and `logout`. Both columns store the time in UNIX format. How can I calculate the total time spent on the network, using as little resources as possible, since the amount of data is quite large?

Answer 1

avg(logout - login)