Re: Question on duplicates

Jayne Heger wrote:
>
> Hiya all,
>
> I have a question on duplicate rows in a database.
>
> What I am having trouble understanding is, if for example, you have a
> primary key value in every relation/table, surely you will have eliminated
> the problem of duplicates? so why the argument?
>
> Or am I missing something?
>
> I just want to make sure I am covering all aspects, and can answer
> questions for when I do my seminar on Wednesday.
>
> Thanks
>
> Jayne
>
> Oh, and another thanks for the people who helped me earlier.

Because some RDBMS allow you to create tables that do not have primary indexes. In fact it is possible to create tables with no indexes.

Although this is contrary to theory indexes are often omitted because lookup performance for very small tables (those which will fit within a single OS physical block) is faster without an index than with an index. Received on Sun Mar 03 2002 - 04:57:14 CET