Analytic troubles

From: Yavor Ivanov <Yavor_Ivanov_at_stemo.bg>
Date: Mon, 10 Nov 2008 11:40:43 +0200
Message-ID: <BD17E2E69E17C64A9684C940EB580E0301102BC74E11@stemodc1.stemo.local>

                Hello, Gurus
                I've been thrown by the developers in an area, which I do not visit frequently. Here is the case:
                Let's say we have a table like this
Date_from                         Name
------------------------------------
01.Nov.2008                      AAA
02.Nov.2008                      AAA
03.Nov.2008                      BBB
04.Nov.2008                      BBB
05.Nov.2008                      BBB
06.Nov.2008                      CCC
07.Nov.2008                      AAA
08.Nov.2008                      AAA

                I need the dates of every change. This is
Date_from         Name
------------------------------------
01.Nov.2008                      AAA
03.Nov.2008                      BBB
06.Nov.2008                      CCC
07.Nov.2008                      AAA

                I can do it with regular SQL, but I make 3 reads of the table:
select distinct name,


                (select min(date_from)

                   from table1 p2
                  where p2.name = p1.name
                    and p2.date_from > (select max(date_from)
                                          from table1 p3
                                         where p3.name != p2.name
                                           and p3.date_from < p1.date_from)) date_from

  from table1 p1
 I'm trying to implement it with analytic functions (and walk through the table only once), but I cannot define the window based on my knowledge. And window definition is not something very explained in the docs... Can someone help me with this?

(Database is 11g on Windows)

Regards,
Yavor Ivanov

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Received on Mon Nov 10 2008 - 03:40:43 CST