Posted by Jerry Stuckle on 05/15/06 04:02

Richard Levasseur wrote:
> FYI - The proper term for a table that solves a many-to-many
> relationship is called an 'intersection tabel'
>

Yes intersection tabel (sic) is one name for them, but describes a subset of
link tables. Link table is another, mutli-to-multi-link table is a third. The
term "link table" has been around since the 1970's. I first heard "intersection
table" in the late 1990's.

> items(item_id, name);
> items2chars(item_id, char_id); <-- intersection table
> characteristics(char_id, name);
>
> In any event, don't store the characteristics in a single field. Put
> them in seperate fields, or create a characteristics table with an
> intersection table.
>

Yes, that is the way to use a link table. You also need to set up foreign keys
on both columns in the link table.

> If a characteristics is only a boolean value, and you don't foresee
> adding/removing attributes, then using fields would work fine (though
> it may make a couple of complicated queries a little tricky).
> If characteristics have attributes themselves, then you need to use the
> intersection method.
> If characteristics you foresee characteristics beinga added/removed, it
> would be better to use the intersection method.
>



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Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
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