我如何将我的子查询的结果与另一个 table 合并？

Question

。尝试 link 将借款人、书籍的结果汇总到 AUTHOR。

期望的结果：

AUTHORID         AUTHORFIRSTNAME      AUTHORLASTNAME
1                     JIM                   SPARKS
2                     JAMES                 ALLEN
3                     MARCUS                RASHFORD
20                    PAUL                  POGBA
22                    THIERRY               HENRY

但我不确定如何 link 返回的顶级 authorids 来检索作者名字和姓氏，但我没有在子查询中提到作者 table

Answer 1

所以，如果我没看错的话，你想做这样的事情：

select authorid, authorfirstname, authorlastname 
 from 
  (select a.authorid, a.authorfirstname, a.authorlastname 
   from author a, borrower b, book c 
   where a.authorid = c.authorid and c.bookid = b.bookid
   and b.borrowdate like '%2017' 
    group by c.bookauthor 
    order by count(*) desc) xx 
 where rownum <=5

Answer 2

您可以在子查询中按 count 的降序将这三个表与 rank() 分析函数连接起来，然后在主查询中取小于等于 5 的值：

SELECT authorid, authorfirstname, authorlastname
  FROM
  (
  SELECT a.authorid, a.authorfirstname, a.authorlastname, 
         rank() over (order by count(*) desc)  as rnk
    FROM AUTHOR a
    LEFT JOIN BOOK bk ON a.authorid = bk.authorid
    LEFT JOIN BORROWER br ON br.bookid = bk.bookid
   WHERE br.borrowdate between date'2017-01-01' and date'2017-12-31'
   GROUP BY a.authorid, a.authorfirstname, a.authorlastname
   )
  WHERE rnk <= 5
  ORDER BY rnk

如果您使用的是 DB 版本 12c+，获取它们会更容易：

SELECT a.authorid, a.authorfirstname, a.authorlastname, 
       rank() over (order by count(*) desc)  as rnk
  FROM AUTHOR a
  LEFT JOIN BOOK bk ON a.authorid = bk.authorid
  LEFT JOIN BORROWER br ON br.bookid = bk.bookid
 WHERE br.borrowdate between date'2017-01-01' and date'2017-12-31'
 GROUP BY a.authorid, a.authorfirstname, a.authorlastname
 ORDER BY rnk 
 FETCH FIRST 5 ROWS WITH TIES

我使用 br.borrowdate between date'2017-01-01' and date'2017-12-31' 而不是 to_char(br.borrowdate) like '%2017' 的地方可以使 borrowdate 列上的索引受益。

return 有关系的行上方的那些查询，例如如果多行与第 5 行的值匹配，它们会带来多于 5 行。

不要使用rownum伪列进行排名，因为它的值是在排序前计算的，可能会产生错误的结果。

我如何将我的子查询的结果与另一个 table 合并？

how do i take the results of my subqueries to join with another table?

sql

oracle

join

subquery

analytic-functions