Re: Using varchar primary keys.

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> Natural Keys have a purpose but when do they exist in the database?
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In my case it's the tags. Table tags has only two columns id and tag. Each
one has a unique index. I have many other similar lookup tables. For
example things like order_status, item_type etc.

> What about the Natural Keys of an external source? Should that be stored
> in a lookup table along with the integer based Surrogate Key?
> Maybe I'll call it "bars_pks".
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I always keep those. The API's I expose to clients and partners allow them
to modify the records they send and I let them refer to items by their own
primary keys. This has always worked out well for me.

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> --Spelling error.
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> UPDATE tags SET tag = 'foo' WHERE tag = 'fu';
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> This will fail unless you ON UPDATE CASCADE.
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Yes of course you'd need the on update cascade. Then again maybe I don't
even need that tags table. Tags could just be a view (select distinct tag
from child_tags). I am not saying that's efficient or desirable but it's
possible.