Getting the first and the last record with analytics

Question

I have a table called horario (time) which has the following columns: card_number,
card_holder_name, card_reader_location and time. I came up with the following sql
statement that gives me the current row and the next row so I can subtract one from
the other and see how much time elapsed between them. As you can see below:
SELECT *
FROM   (SELECT card_number,
               reader card_reader_location,
               hora TIME,
               lead(reader) over(PARTITION BY card_number ORDER BY hora) next_card_reader_location,
               lead(hora) over(PARTITION BY card_number ORDER BY hora) next_time_action
        FROM   horario
        WHERE  card_number = '26965'
        AND    to_char(hora, 'DD-MON-YYYY') =
               to_date('03-JAN-2006', 'DD-MON-YYYY')
        GROUP  BY card_number,
                  reader,
                  hora)
CARD_NUMBER               CARD_READER_LOCATION                               TIME                 NEXT_CARD_READER_LOCATION                          NEXT_TIME_ACTION                                                                                                                                      
26965                     BASEMENT DOOR READER  IN                           03-JAN-2006 07:26:00 BASEMENT DOOR READER  OUT                          03-JAN-2006 14:44:00                                                                                                                                  
26965                     BASEMENT DOOR READER  OUT                          03-JAN-2006 14:44:00 BASEMENT DOOR READER  IN                           03-JAN-2006 14:45:00                                                                                                                                  
26965                     BASEMENT DOOR READER  IN                           03-JAN-2006 14:45:00 BASEMENT DOOR READER  OUT                          03-JAN-2006 16:07:00                                                                                                                                  
26965                     BASEMENT DOOR READER  OUT                          03-JAN-2006 16:07:00                                                                                                                                                                                                           Now I need to come up with a sql query that will subtract the time field of the very
last row (16:07:00) and the time field of the very first row (07:26:00) so I know how
many hours were worked on that specific date. Can I do that using analytics ? If so,
how ?
thanks !
gleisson henrique

Answer 1

In a way you can get those min/max dates in the same row and subract them in the outer select just like this
SELECT *
FROM (SELECT card_number,
reader card_reader_location,
hora TIME,
lead(reader) over(PARTITION BY card_number ORDER BY hora) next_card_reader_location,
lead(hora) over(PARTITION BY card_number ORDER BY hora) next_time_action
max(hora) over(PARTITION BY card_number) max_hora,
min(hora) over(PARTITION BY card_number) min_hora
FROM horario
WHERE card_number = '26965'
AND to_char(hora, 'DD-MON-YYYY') =
to_date('03-JAN-2006', 'DD-MON-YYYY')
GROUP BY card_number,
reader,
hora)