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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Tricky query question
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 <ORACLE-L_at_fatcity.com>
<djordjej_at_roge cc:
rs.com> Subject: Re: Tricky query question
Sent by:
root_at_fatcity.c
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
> 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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-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Djordje Jankovic INET: djordjej_at_rogers.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<---->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Privileged/Confidential information may be contained in this message. If you are not the addressee indicated in this message (or responsible for delivery of the message to such person), you may not copy or deliver this message to anyone. In such case, you should destroy this message and kindly notify the sender by reply e-mail or by telephone on (61 3) 9612-6999. Please advise immediately if you or your employer does not consent to Internet e-mail for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of Transurban City Link Ltd shall be understood as neither given nor endorsed by it. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<---->>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Mark Richard INET: mrichard_at_transurban.com.au Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Thu Jan 23 2003 - 23:38:51 CST
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