Here's a more complex example for sessionizing user events: # specify the target SQL dialect prql target:sql.duckdb # define the "sessionize"

Here's a more complex example for sessionizing user events: # specify the target SQL dialect prql target:sql.duckdb # define the "sessionize" function let sessionize = func user_col date_col max_gap:365 tbl<relation> -> ( from tbl group user_col ( window rows:-1..0 ( sort date_col derive prev_date=(lag 1 (date_col|as date)) ) ) derive { date_diff = (date_col|as date) - prev_date, is_new_session = case [date_diff > max_gap || prev_date==null => 1, true => 0], } window rows:..0 ( group user_col ( sort {date_col} derive user_session_id = (sum is_new_session) ) sort {user_col, date_col} derive global_session_id = (sum is_new_session) ) select !{prev_date, date_diff, is_new_session} ) # main query from invoices select {customer_id, invoice_date} sessionize customer_id invoice_date max_gap:365 sort {customer_id, invoice_date} You can also try that in the playground: https://prql-lang.org/playground/ https://prql-lang.org/playground/