Djorde (and Maria),
You are correct... I should have explained that this is a history type
table so the field I referred to as "primarykey" is not the primary key of
this table. Thanks for your tip and the one from Maria - I will look at
them both in detail next week. The actual process using this statement
will be dealing with about 1.5 million instances of "primarykey" however it
must perform in small batches so I'll be comparing both approaches from a
performance perspective.
Thanks,
Mark.
"Djordje
Jankovic" To: Multiple recipients of list ORACLE-L
<[EMAIL PROTECTED]>
<djordjej@roge cc:
rs.com> Subject: Re: Tricky query question
Sent by:
[EMAIL PROTECTED]
om
24/01/2003
16:05
Please respond
to ORACLE-L
Is "primarykey" really a primary key for the table: you say "there might be
50 records for the primary key", or the table's PK is
(primarykey,dateinserted) ?
If the primary key is not the table's PK, I guess a query along the
following lines will give you what you want:
select t1.primarykey, t2.status, t2.dateinserted
from (select primarykey, status, dateinserted from tab) t1
, (select primarykey, status, dateinserted from tab) t2
where t1.primarykey = t2.primarykey
and t1.dateinserted < t2.dateinserted
and t1.dateinserted = (select max(dateinserted)
from tab t3
where t3.primarykey = t2.primarukey
and t3.dateinserted <
t2.dateinserted)
and t1.status <> t2.status
Djordje
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]>
Sent: Thursday, January 23, 2003 10:34 PM
> Hi All,
>
> This is a question for those who like writing tricky queries as a single
> SQL...
>
> Assume I have a table with the following structure (imaginary table to
keep
> example simple):
>
> primarykey number(8)
> status char(1)
> dateinserted date
> <many other fields which are insignificant>
>
> A row is inserted into this table any time one, or more, fields change
for
> the record. What I'm trying to determine is the "dateinserted" for each
> time the value of "status" changed - remembering that there might be 50
> records for the primary key and five of those include a change in status
-
> I want the dates of those five records (plus the value of status at each
> date).
>
> Is there any way to achieve this within a single SQL statement? I
realise
> that I could cursor through each record in date order and use a variable
to
> store the previous value of status - but I'd love to compress this to a
> single statement. I've seen the syntax "OVER" used in some queries and
> suspect this may be useful but I really don't understand it enough to
know.
>
> Thanks in advance if you can help me on this one,
>
> Mark.
>
> PS: Sorry if this appears more than once - I've been getting mail server
> failures all day
>
>
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