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    <p>Edited based on comments. Say you're searching for articles that:</p> <ul> <li>Have a keyword named 'a1'</li> <li>Or, have both keywoards named 'b1' and 'b2'</li> <li>Or, have either keyword 'c1', 'c2' or 'c3'</li> </ul> <p>You can query like:</p> <pre><code>select a.id from Articles a inner join ArticleKeywords ak on ak.articleid = a.id inner join Keywords k on k.id = ak.keywordid group by a.id having sum(case when k.name in ('a1') then 1 else 0 end) = 1 or sum(case when k.name in ('b1','b2') then 1 else 0 end) = 2 or sum(case when k.name in ('c1','c2,'c3') then 1 else 0 end) &gt; 0 </code></pre> <p>Per SquareCog's comment, you can greatly increase performance with an early WHERE clause. The clause would limit the grouping to the relevant keywords only. In the above query, add the WHERE just before the HAVING:</p> <pre><code>... inner join Keywords k on k.id = ak.keywordid where k.name in ('a1','b1','b2','c1','c2','c3') group by a.id ... </code></pre> <p>You can retrieve the other details of the article(s) like:</p> <pre><code>select * from Articles where id in ( ...query from above here... ) </code></pre> <p>Say you have a table that contains groups to search for, defined like:</p> <pre><code>groupid - keywordid 1 - 1 1 - 2 2 - 3 </code></pre> <p>Meaning the article has to match ((keyword 1 and keyword2) or keyword3). Then you can query like this:</p> <pre><code>select ak.articleid from ArticleKeywords ak inner join Search s on ak.keywordid = s.keywordid group by s.searchgroup, ak.articleid having count(*) = ( select count(*) from #Search s2 where s2.Searchgroup = s.SearchGroup ) </code></pre>
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    1. COThis is where it gets complicated, because the number of keywords is unknown and not limited. Maybe I'm expecting too much!
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    2. COThanks. The problem with that is there might be sets of words with 1, 2, 3 or more words that must appear together, so the having part is going to restrict those possibilities.
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    3. CONicely done, Andomar. For efficiency, one would still want to throw in a 'where k.keyword in....' so that you can filter out the irrelevant section before doing the group-by or the join.
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