giving priority to values in an SQL stmt

is there any way i can do a query to specify that I want to give priority to some value?

for instance i have:

SELECT TOP (20) 
  r.MD5, r.Title, r.Link, t.Category, t.tfidf, COUNT(r.MD5) AS matching_terms
FROM 
  Resource AS r INNER JOIN tags AS t ON r.MD5 = t.MD5
WHERE        
  (t.Category IN ('algorithm', 'k-means', 'statistics', 'clustering', 'scien开发者_Go百科ce'))

GROUP BY r.MD5, r.Title, r.Link, t.Category, t.tfidf
ORDER BY matching_terms DESC, t.tfidf DESC

i want that 'algorithm' is given higher priority when finding results. any ideas?

I'm not sure how high a priority you want to make 'algorithm', but in any case, you can add this to the ORDER BY clause, in order to make it the most important category (all other categories are equally important):

ORDER BY ..., CASE t.Category = 'algorithm' THEN 0 ELSE 1 END, ...

If however your concept of "priority" is somehow correlated with the importance of the matching_terms expression, you could also try something like this (you'd have to nest your above select)

SELECT TOP(20) FROM (
  [your original select without TOP(20) clause]
)
ORDER BY (matching_terms * CASE t.Category = 'algorithm' 
                           THEN 1.5 ELSE 1 END) DESC, t.tfidf DESC

But that's just an example to give you an idea.

UPDATE: Following you comment, you can generate a case statement like this:

ORDER BY CASE t.Category WHEN 'algorithm'  THEN 0
                         WHEN 'k-means'    THEN 1
                         WHEN 'statistics' THEN 2
                         WHEN 'clustering' THEN 3
                         WHEN 'science'    THEN 4 END

Or alternatively (especially if your list of categories is large), then you should add a sort field to tags, containing the priority. Then you could simply order by sort

SELECT        TOP (10) r.MD5, r.Title, r.Link, t.Category, t.tfidf, COUNT(r.MD5) AS matching_terms
FROM            Resource AS r INNER JOIN
                         tags AS t ON r.MD5 = t.MD5
WHERE        (t.Category IN ('astrophysics', 'athletics', 'sports', 'football', 'soccer'))
GROUP BY r.MD5, r.Title, r.Link, t.Category, t.tfidf
ORDER BY (CASE t .Category WHEN 'astrophysics' THEN 0 WHEN 'athletics' THEN 1 WHEN 'sports' THEN 2 WHEN 'football' THEN 3 WHEN 'soccer' THEN 4 END)

Thanks for giving me the idea Lukas Eder