Re: Analytic troubles
- From: Ian Cary <ian.cary@xxxxxxxxxxxxxx>
- To: Yavor_Ivanov@xxxxxxxx
- Date: Mon, 10 Nov 2008 10:15:46 +0000
This does the trick for the example data
select date_from,name
from
(
select date_from,
name,
lag(name) over (order by date_from) last_name
from tab1
)
where last_name != name
or last_name is null;
DATE_FROM NAME
--------- ----------
01-NOV-08 AAA
03-NOV-08 BBB
06-NOV-08 CCC
07-NOV-08 AAA
Cheers,
Ian
|---------+----------------------------->
| | Yavor_Ivanov@stemo|
| | .bg |
| | Sent by: |
| | oracle-l-bounce@fr|
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| | 10/11/2008 09:40 |
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>--------------------------------------------------------------------------------------------------------------|
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| To: oracle-l@xxxxxxxxxxxxx
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| cc:
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| Subject: Analytic troubles
|
>--------------------------------------------------------------------------------------------------------------|
??????????????? 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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