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如果没有集合运算符，我如何才能找到任何涵盖三个不同 SQL 系统中的两个的书籍。我正在使用三个主题 id 'SSRV'、'ORA'、'MySQL' 并且需要输出任意三个中的 2 个。例如，这本书可能有一个主题 SSRV 和一个 ORA 主题，但没有 MySQL。这些主题的任何两个组合都足以通过我们的过滤器。

我想显示符合此测试的书籍的 book_id 和标题。

  SELECT book_id
       , title
    FROM a_bkinfo.books B
   WHERE book_id IN (
       SELECT book_id
         FROM a_bkinfo.book_topics BT
    WHERE topic_id = 'SSRV' )
  AND book_id IN (
       SELECT book_id
         FROM a_bkinfo.book_topics BT
    WHERE topic_id = 'ORA' )
  AND book_id IN (
       SELECT book_id
         FROM a_bkinfo.book_topics BT
    WHERE topic_id = 'MySQL' )
  AND book_id IN (
        SELECT COUNT(*) 
                   FROM (  
                       SELECT book_id
                           ,  count(topic_id) AS topics
                         FROM a_bkinfo.book_topics BT 
                        GROUP BY book_id
                        HAVING count(topic_id) = 2
                        ) t 
              ;

更新后的版本：

   SELECT book_id
 , title
 FROM a_bkinfo.books B
 WHERE book_id IN (
       SELECT book_id
         FROM a_bkinfo.book_topics BT
    WHERE topic_id ='SSRV'
        OR topic_id ='ORA' )
AND book_id IN (
        SELECT book_id
          FROM a_bkinfo.book_topics BT
    WHERE topic_id ='SSRV' 
        OR topic_id ='MySQL')
AND book_id IN (
        SELECT book_id
          FROM a_bkinfo.book_topics BT
    WHERE topic_id ='ORA' 
        OR topic_id ='MySQL');
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1 回答 1

0 
SELECT b.book_id, b.title, COUNT(*) FROM books b
INNER JOIN book_topics bt ON (b.book_id = bt.book_id)
GROUP BY b.book_id, b.title
HAVING COUNT(*) = 2

如果在 book_topics 中每个书-主题关系只有一行，这将起作用。这些对也必须是唯一的。如果您的数据不符合要求，则需要更复杂的查询。
更新
由于 book_id 是唯一的唯一标识符，而不是新版本： 

SELECT b.book_id FROM books b
INNER JOIN book_topics bt ON (b.book_id = bt.book_id)
GROUP BY b.book_id
HAVING COUNT(topic_id) = 2

要求与上述相同。

于 2013-11-11T04:33:12.887 回答