Hi, I am trying to run a recursive cte query on temporal data. I attach the starting set (temp_station) and the solution set (temp_solution)
A user visits many stations in random order. They can enter a station many times but they only exit once. After they enter a station X, they can enter other stations or exit other stations, i.e. a station entry/exit can fully contain other stations) but eventually they will exit station X (these are invalid visits to other stations within an entry/exit context for a single station.) They can validly visit a station multiple times but these visits must not overlap with each other. The objective is to list the earliest entry time and matching exit time for each valid visit to a station according to the rules above. My attempt below doesn't recurse and I can't understand what I need to do here. Can anyone shed some light on this? Regards Liam --drop table temp_station; create table temp_station ( station_id int ,movement_direction varchar(5) ,event_tick char(3) ,event_time timestamp with time zone ); delete from temp_station; insert into temp_station (station_id, movement_direction, event_tick, event_time) values (1, 'enter', 't01', '2012-10-18 10:23:31'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (1, 'enter', 't02', '2012-10-18 10:31:42'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (1, 'enter', 't03', '2012-10-18 10:41:41'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (1, 'exit', 't04', '2012-10-18 10:48:34'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't05', '2012-10-18 10:54:57'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't06', '2012-10-18 11:01:35'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (3, 'enter', 't07', '2012-10-18 11:10:52'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (3, 'enter', 't08', '2012-10-18 11:20:50'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (4, 'enter', 't09', '2012-10-18 11:29:56'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (3, 'enter', 't10', '2012-10-18 11:37:53'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (7, 'exit', 't11', '2012-10-18 11:44:42'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (3, 'exit', 't12', '2012-10-18 11:53:14'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (4, 'enter', 't13', '2012-10-18 12:02:59'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (4, 'enter', 't14', '2012-10-18 12:12:11'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (4, 'exit', 't15', '2012-10-18 12:20:29'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't16', '2012-10-18 12:26:57'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't17', '2012-10-18 12:34:12'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (9, 'exit', 't18', '2012-10-18 12:40:10'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't19', '2012-10-18 12:48:29'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (5, 'enter', 't20', '2012-10-18 12:54:37'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (5, 'exit', 't21', '2012-10-18 13:00:42'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't22', '2012-10-18 13:06:09'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't23', '2012-10-18 13:15:47'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'exit', 't24', '2012-10-18 13:23:34'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't25', '2012-10-18 13:29:22'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't26', '2012-10-18 13:37:27'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (5, 'exit', 't27', '2012-10-18 13:45:02'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'exit', 't28', '2012-10-18 13:53:44'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (7, 'enter', 't29', '2012-10-18 14:00:09'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (7, 'enter', 't30', '2012-10-18 14:08:45'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (8, 'enter', 't31', '2012-10-18 14:14:12'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (8, 'exit', 't32', '2012-10-18 14:20:20'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (7, 'exit', 't33', '2012-10-18 14:28:23'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't34', '2012-10-18 14:35:43'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't35', '2012-10-18 14:44:34'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (8, 'enter', 't36', '2012-10-18 14:51:26'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (8, 'enter', 't37', '2012-10-18 14:59:08'); insert into temp_station (station_id, movement_direction, event_tick, event_time) values (8, 'exit', 't38', '2012-10-18 15:06:10'); --drop table temp_solution; create table temp_solution ( station_id int ,movement_direction varchar(5) ,event_tick char(3) ,event_time timestamp with time zone ); delete from temp_solution; insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (1, 'enter', 't01', '2012-10-18 10:23:31'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (1, 'exit', 't04', '2012-10-18 10:48:34'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't05', '2012-10-18 10:54:57'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't06', '2012-10-18 11:01:35'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (3, 'enter', 't07', '2012-10-18 11:10:52'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (3, 'exit', 't12', '2012-10-18 11:53:14'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (4, 'enter', 't13', '2012-10-18 12:02:59'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (4, 'exit', 't15', '2012-10-18 12:20:29'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't16', '2012-10-18 12:26:57'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't19', '2012-10-18 12:48:29'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (5, 'enter', 't20', '2012-10-18 12:54:37'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (5, 'exit', 't21', '2012-10-18 13:00:42'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't22', '2012-10-18 13:06:09'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (6, 'exit', 't24', '2012-10-18 13:23:34'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't25', '2012-10-18 13:29:22'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (6, 'exit', 't28', '2012-10-18 13:53:44'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (7, 'enter', 't29', '2012-10-18 14:00:09'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (7, 'exit', 't33', '2012-10-18 14:28:23'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't34', '2012-10-18 14:35:43'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't35', '2012-10-18 14:44:34'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (8, 'enter', 't36', '2012-10-18 14:51:26'); insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (8, 'exit', 't38', '2012-10-18 15:06:10'); with recursive enter_event as ( select row_number() over(order by event_time) as rownum, * from temp_station where movement_direction = 'enter' --and station_id in (7, 8) ) ,exit_event as ( select row_number() over(order by event_time) as rownum, * from temp_station where movement_direction = 'exit' --and station_id in (7, 8) ) ,event_period as ( select a.rownum, a.station_id, a.event_tick as start_tick, b.event_tick as end_tick, a.event_time as start_time, b.event_time as end_time from enter_event a join exit_event b on a.station_id = b.station_id -- entry always before exit and a.event_time < b.event_time ) ,dtr (rownum, station_id, start_tick, end_tick, start_time, end_time) as ( select rownum, station_id, start_tick, end_tick, start_time, end_time from event_period where start_tick = (select min(start_tick) from event_period) union all select a.rownum, a.station_id, a.start_tick, a.end_tick, a.start_time, b.end_time from event_period a ,dtr b where a.end_time < b.start_time and a.start_time < a.end_time and b.start_time < b.end_time ) select * from dtr