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Back in lesson one and two,
one of the tables in the zoo database we

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talked about, was the diet table which
describes which foods each species eats.

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We looked at three ways we could store
multiple foods, for a single species.

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As multiple food columns and

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one row per species, as a single
column with foods separated by commas.

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And has separate rows, for
each food comma species pair and

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I mentioned that this form, has some
big advantages over the other two.

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It works better with drawings,
it works better in comparisons and

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you don't have to know in advance how
many foods there are, and we also looked

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at these two tables of donors to
the zoo and their phone numbers.

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In order to avoid duplication,
we split the information that

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was in one object or it's record,
into two separate tables.

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In database jargon,
these are called normalized forms and

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the others are denormalized forms.

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Normalization is the central
idea in database design.

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Normalizing involves making
the relationships among the tables in

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your database, match the relationships
that are really there amongst

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the various pieces of data.

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There's a bunch of database
theory behind this idea.

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I put a link in the instructor notes to
a paper with lots of details about it.

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Up ahead, I'll just tell you
the most relevant highlights.