Hi Willem,
Il giorno 30/gen/08, alle ore 22:15, Willem Buitendyk ha scritto:
I'm trying to replicate the use of Oracle's 'lag' and 'over
partition by' analytical functions in my query. I have a table
(all_client_times) such as:
client_id, datetime
122, 2007-05-01 12:00:00
122, 2007-05-01 12:01:00
455, 2007-05-01 12:02:00
455, 2007-05-01 12:03:00
455, 2007-05-01 12:08:00
299, 2007-05-01 12:10:00
299, 2007-05-01 12:34:00
and I would like to create a new view that takes the first table and
calculates the time difference in minutes between each row so that
the result is something like:
client_id,datetime, previousTime, difftime
122,2007-05-01 12:01:00, 2007-05-01 12:00:00, 1
455,2007-05-01 12:03:00, 2007-05-01 12:02:00, 1
455,2007-05-01 12:08:00, 2007-05-01 12:03:00, 5
299,2007-05-01 12:34:00, 2007-05-01 12:10:00, 24
I'd create a "previousTime" column and manage it using a trigger.
Anyway, it depends on the time-dependancy of the table
Then you can perform "temporal" in a much easier way.
You could be interested in taking a look at the following link
http://www.cs.arizona.edu/~rts/tdbbook.pdf
Cheers,
e.
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