Question

如何在没有set运算符的情况下找到任何涵盖三种不同sql系统中的两种的书籍。我正在使用三个主题ID'SSRV'，'ORA'，'MySQL'，需要输出任意三个中的2个。例如，本书可能有一个SSRV主题和一个ORA主题，但不是MySQL。这两个主题的任意两个组合足以通过我们的过滤器。我想显示符合此测试的book_id和书名。我完全迷失了。

  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');

Answer 1

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book_topics中每个图书 - 主题关系只有一行，这将有效。这些对也需要是唯一的。如果您的数据不符合要求，则需要更复杂的查询的更新
由于book_id是唯一的唯一标识符，因此是新版本：

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。

有人可以用这个子查询来帮助我吗？

1 个答案: