Re: data warehousing desing - to denormalize or not to denormalize -

• Gurelei <gurelei_at_yahoo.com> on 05/10/02 10:43:23 -0800

> Hi.
>
> We are designing a small database using a data
> warehousing desing. We have created a 3rd normal form
> and are now debating whether and how to denormalize
> it. I see the pluses of denormalization - easier
> queries creation and tuning. What are the
> disadvantages that we should be aware of? Wasted space
> is not an issue because the tables a pretty small.
> What else should we consider as a potential issue?

Oracle was designed (and still is) an OLTP tool. It doesn't do very well with fully denormalized data. Wasted space is only one problem, bloated indexes are another. You can also end up with indexes that lack enough entropy for general use due to repatition, leaving you better off with table scans in most cases.

For a small(ish) database there may not be any real difference between a snowflake and star schema, but databases tend to grow. Every time I've dealt with any denormalized schemas in Oracle they have performed poorly (or crashed).

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