NYCPHP Meetup

[tedd]

At 8:13 AM -0400 9/1/09, Dan Cech wrote:
>Michael Southwell wrote:
>>  It's always seemed easier and clearer to me to use WHERE instead of JOIN
>>  (where the table IDs are indeed named id, and the foreign keys are
>>  labeled with the table name):
>>
>>  SELECT product_name, vendor_name
>>  FROM product, vendor
>>  WHERE vendor.id = product.vendor_id
>
>The problem with this approach is that you end up with the join
>conditions and the 'real' selection criteria mashed together.
>
>SELECT product_name, vendor_name, category_name
>FROM product, vendor, category
>WHERE vendor.id = product.vendor_id AND price > 50 AND category.id =
>product.category_id AND color = 'red'
>
>vs
>
>SELECT product_name, vendor_name, category_name
>FROM product
>JOIN vendor ON vendor.id = product.vendor_id
>JOIN category ON category.id = product.category_id
>WHERE price > 50 AND color = 'red'
>
>I mixed up the order of the WHERE elements in the first query for the
>purposes of this example, but I have seen stuff like that in production
>code.
>
>Dan

Dan:

I need to understand joins much better than I do now because the 
first query I fully understand while the second I don't.

Cheers,

tedd
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