Most Active User Stats

What I want to do is pull a list of online users from a file on my webserver (i will maintain the file and can make it show with tags before and after the username if that helps). I want these usernames to be added to a mysql database and if the username isn't already in there then to add it. I want to track how active each user is. I am ok with something like a database that just has the date and a tally count in minutes, so for example today is 6/5/2018 if i pull the user list every 15 minutes then the value associated to todays date of 6/5/2018 will have +15 added to it. I am just a novice coder so if you have a better way to hold a ton of activity data let me know. I then want to have a website that shows a list of the online users sorted by most minutes online in the last 7 days but also show the stat for minutes online in the last 30 days. I picture it going like this: Code grabs userlist, checks if username is already in the database, if its not then it adds the username. It then checks to see if todays date is already in the database if not then it creates the table (or whatever its called) for todays date . The value of +15 is added to todays date to signify 15 minutes as the code should run every 15 minutes (I may change the frequency in the future). I figure i'll put this in a cronjob or something that runs every 15minutes? I also want separate code for me to be able to search a username and have it calculate the number of minutes spent online in the last 7 days and last 30 days.