Re: Is this De-Normalization?

"tom dorgan" <tdorgan_at_yahoo.com> wrote in message <news:d4518ef4.0312011036.311b9a1a_at_posting.google.com>...

> We have a table, call it DataParent. Another table, call it
> DataChildren, contains foreign keys to DataParent. You get the idea
> that this is a one-to-many relationship like the well-known Order and
> LineItem pair.
>
> In a discussion regarding increasing performance, the idea was brought
> up to pull each of the DataChildren items into the DataParent table by
> using a fixed number of columns, call them DataChildren1-N in
> DataParent. Leave unused slots null and only allow N DataChildren per
> DataParent.

This way madness lies. Will these DataChildren1-N hold keys for rows in DataChildren, or is DataChildren going away entirely?

> I understand this to be First Order de-normalization - we are putting
> an array, set or tuple into a table. I was told that this was not the
> case but did not get an explanation.

I've heard of one case where something similar /may/ be justified, an items-for-sale table with a child table holding price histories. The /current/ price was copied, not moved, into the parent table, with triggers to keep the copy synchronized with the price history.

--
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