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Posted by Steve Kass on 08/29/05 20:09
Hugo,
As usual, you have said nothing that isn't correct and
helpful here...
SK
Hugo Kornelis wrote:
> On 27 Aug 2005 08:50:45 -0700, coosa wrote:
>
>
>>Your logic is quite interesting and i'd like to learn much from you.
>>First, select '%'+@search_key1+'%' or select '%'+@search_key2+'%' etc.
>>would bring some results, then why do you write "where NOT exists"?
>
>
> Hi Coosa,
>
> Remember back at school, when your English teacher told you: "Don't use
> no double negations, not never"?
>
> He was wrong.
>
> I didn't take the time to go over all details in Steve's post, but at
> first glance it lloks just like the "relational division" I mentioned in
> my previous post.
>
> You wanted to find items that satisfy all search terms. Steve put the
> search terms in a derived table, then went on to use the standard
> solution for finding a match that satisfies all rows - by rephrasing it
> with a double negation:
>
> "Find items that match all search terms" --> "Find items for which there
> is no search term that it doesn't match".
>
> Hence the use of not one but actually _TWO_ not exists conditions.
>
> Best, Hugo
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