Activity
table to include only the rows where activity_date
is within the 30-day period ending on '2019-07-27'.user_id
and count the distinct session_id
for each user to get the number of sessions per user.IFNULL
function to handle cases where there might be no sessions, and default the value to 0.00.ROUND
function to round the average to two decimal places.erDiagram Activity { int user_id int session_id date activity_date enum activity_type }