Querying a "chronologically ordered table"

Question

Hi,
I'm not very familiar with joining tables ... My problem is: Given two tables A / B with essentially these columns (ballast omitted):
A.ID number (pk)
A.BEGIN date
B.ID number (pk)
B.FK_A number references A ( ID )
B.END date
B.DATA ...
(the ID's are taken from a sequence and therefore should be numeric). Imagine B as "history of data" of some objects A, e.g. A as "people" and B as "peoples' addresses over time" or something like that, with every move resulting in an update of the "last" B.END with the date of the move and inserting a new row into B.
I often have to find
- the one row of B valid on a date D (or NULL, if D > A.BEGIN or D < "max( B.END )")
- and / or the "last" (if any) begin preceding D, i.e. the value "nvl( max( B.END + 1 ), A.BEGIN ) <= D" (obviously pseudo coded ...)
given some A.ID. Now what is the "cheapest" means to get this row or value? Any "static assistance" (views, ...) or data or type restriction (like "B.END not null") to keep statements straightforward would be okay, as long as they don't decrease performance too much.
It would be nice to have an ANSI-SQL solution, but if some Oracle means could boost this drastically, I wouldn't ban these a priori ;>.
Thx very much!
Harald

Answer 1

Hi Dave,
thank you very much, this is exactly what I was searching for (and - by the way - you finally brought me to learn about analytic functions ... thank you for this too).
Um, rather a comment than another question: I couldn't find anything exploitable and pertinent for "overlaps" and "between". Assuming these to be operators I searched "[master index|http://download-west.oracle.com/docs/cd/B14117_01/mix.101/b12039/toc.htm]" and "contents" of Oracle® Database SQL Reference 10g Release 1 (10.1), but they're not listed there - ???
Harald
Edited by: harald.fischer on 21.11.2008 03:51