Re: Normalization of attributes

Jonathan Lewis wrote:
>
> Should 'abcxx' match 'abcyy' ?
> Your example is much more precise
> than your general statement.

Well, yes and no. 'abcxx' and 'abcyy' should be treated as same entries, but in practice there should be no such combination. We can assume that the prefix from T1 will be fully in T2 and vice versa, so
that 'abc' match 'abcxx'.

>
> Also do you have any high-precision
> access method for either table, or is
> this the only condition that will be applied.

This is the only condition in the where clause. Both rows have an unique index.

>
> Finally, how large is large, and what is
> the time-scale you are aiming at ?

1e+6 in one and 1e+4 records in the other table. As for a time-scale there are two cases. First case is online-decision support. After the user hits return, he wants to know whether the value is in the larger table or not. The second case is when the user loads the smaller table and after a reasonable time wants to know which records are or are not in the table. A flag will be set in the smaller table for further processing.

Peter
>
> --
>
> Jonathan Lewis
> Yet another Oracle-related web site: http://www.jlcomp.demon.co.uk
>
> Peter Balon wrote in message <38220929.6FE2F27B_at_stud.uni-frankfurt.de>...
> >Hello,
> >
> >I am looking for a way to improve search and comparison speed on large
> >tables. The problem is that I have to compare two strings which might
> >have different length. I need to check if the prefixes are equal so that
> >
> > T1.'abc' = T2.'abcd'
> >and
> > T1.'abcd' = T2.'abc'
> >
> >from both ends, with T1 and T2 as tables.
> >Are there some known normalization techniques which I could apply?
> >We are using Oracle 7.3 and will move to 8.x someday.
> >
> >Any comments would be greatly appreciated.
> >
> >thanks in advance
> >
> >Peter Balon
> >
> >
Received on Mon Nov 08 1999 - 17:56:38 CST