多词搜索查询

Question

I have a crawler which scans all the words in a web page. it then inserts each word into a mysql database along with what url it belongs in. The search is then ranked by the amount of words found in the document. The problem is...how do i add multiple term query into my existing query.

It is perfect for single term querying, but i want my query to try and find words together in the same web page, and if neither word appears in the web page, return results for the terms as normal.

My query is below:

         $results = addslashes( $_POST['results'] );

               " SELECT p.page_url AS url,
                       COUNT(*) AS occurrences 
                       FROM page p, word w, occurrence o
                       WHERE p.page_id = o.page_id AND
                       w.word_id = o.word_id AND
                       w.word_word = \"$keyword\"
                       GROUP BY p.page_id
                       ORDER BY occurrences DESC
                       LIMIT $results"

Answer 1

Use COUNT(DISTINCT ...) to count the number of different words found on each page, and use IN to find any of a list of words:

SELECT
    p.page_url AS url,
    COUNT(DISTINCT w.word_word) AS words_found
    COUNT(*) AS occurrences 
FROM page p
JOIN occurrence o ON p.page_id = o.page_id
JOIN word w ON w.word_id = o.word_id
WHERE w.word_word IN ('foo', 'bar')
GROUP BY p.page_id
ORDER BY occurrences DESC

If you want to ensure that at least n of the search terms are on the page then add a HAVING clause:

GROUP BY p.page_id
HAVING COUNT(DISTINCT w.word_word) >= 2
ORDER BY occurrences DESC

Answer 2

You can do sub-selects if the DB engine supports it. Example:

SELECT 
  url, 
  (select count(*) from table where conditions1) as count1, 
  (select count(*) from table where conditions2) as count2 
 FROM table