SQL query to turn audit trail in / out times to list of locations

Question

I have a database that is used to track the location of physical objects, lets call them widgets. It has an audit trail table that tracks when a widget is put in a location, and when it leaves a location (and where it went after that).

So conceptually it looks like this

Widget ID   Date           Old Location   New Location
1           01-Oct-2013    NULL           101
1           03-Oct-2013    101            108
1           08-Oct-2013    108            101
2           01-oct-2013    NULL           101
2           02-Oct-2013    101            103
3           12-oct-2013    NULL           101

I want to be able to query a list of which widgets were in location 101 between a start and end date, such as 08-09 Oct 2013, this should be widget 1 but not widget 2 or 3.

I'm not sure how to get all these cases. I can pull a list of widget's that were moved in before the end, and a list of widgets that were moved out before the start, but that would also eliminate widget 1 as it leaves and comes back.

I think I need to convert this to a table with widget, location, entry date and exit date, but I'm not sure how to do that ?

EDIT: As pointed out, My data was wrong, I've updated to make the question the 8th to 9th (it was the 4th to 5th). So Widget 1 is the only widget in location 101 in that period.

Answer 1

Try something like this:

select *
from
(select "Widget ID" id, 
"New Location" loc,
"Date" start_date, 
lead("Date", 1, sysdate) over (partition by "Widget ID" order by "Widget ID") end_date
from widgets) t
where t.loc = 101
and start_date < <<your_ending_date>> and end_date > <<your_starting_date>> 

here is a sqlfiddle demo (note that I changed you data a little bit)

Answer 2

So you need last state of each widget within period.
Probably need subselect statement that selects all widgets between dates, groups them by id, orders by Date desc, selects top 1, so you know widget's last state within the period.

UPDATE according to new conditions

I want to know if the widget was in the location at any time during the period

You make select with distinct IDs and a subselect with EXISTS that checks if the row with the current ID and date within period and new location = X presents in resultset. This will make you know what items came to store at least 1 time.