Question

所以我有一个问题：查找每位作者写的最新书籍。这是我正在使用的表：

这是预期的输出

到目前为止，我得到的是：

select unique fname || ' ' || lname "Author", max(pubdate) "Date 
Pub"
from books join bookauthor using (isbn)
join author using (authorid)
group by fname, lname
order by 2,1;

这给了我输出

Author            Date Pub
--------------------- ---------
JUAN ADAMS        04-JUN-03
TINA PETERSON     04-JUN-03
JACK BAKER        17-JUL-04
OSCAR FIELDS      17-JUL-04
LISA PORTER       21-JAN-05
WILLIAM WHITE     21-JAN-05
LISA WHITE        01-MAY-05
ROBERT ROBINSON   08-NOV-05
JAMES AUSTIN      31-DEC-05
JANICE JONES      01-MAR-06
TAMARA KZOCHSKY   18-MAR-06
SAM SMITH         11-NOV-06

问题是，当我在查询中添加标题时，会显示每个标题，而不仅仅是显示最近发布的标题。

select unique fname || ' ' || lname "Author Name", title , pubdate
from books join bookauthor using (isbn)
join author using (authorid)
order by 1,2;

Author Name           TITLE                      PUBDATE
--------------------- ------------------------------ ---------
JACK BAKER            COOKING WITH MUSHROOMS     28-FEB-04
JACK BAKER            PAINLESS CHILD-REARING     17-JUL-04
JAMES AUSTIN          DATABASE IMPLEMENTATION    04-JUN-03
JAMES AUSTIN          HOLY GRAIL OF ORACLE       31-DEC-05
JANICE JONES          E-BUSINESS THE EASY WAY    01-MAR-06
JANICE JONES          REVENGE OF MICKEY          14-DEC-05

Answer 1

以这种方式尝试：

select unique fname || ' ' || lname "Author Name", title , pubdate
from books b
where isbn in (
  select ba.isbn from (
    select ba.isbn from bookauthor ba
    join author a using (authorid)
    order by pubDate
    LIMIT 1
  )t
)
order by 1,2;

Answer 2

对于MySQL 8.0（或几乎任何版本的Oracle），使用ROW_NUMBER()可以很简单：

SELECT * FROM (
    SELECT
        CONCAT(a.fname, ' ', a.lname),
        b.title,
        b.pubdate,
        ROW_NUMBER() OVER(PARTITION BY b.authorid ORDER BY b.pubdate DESC) rn
    FROM
        books b
        JOIN bookauthor ba using (isbn)
        JOIN author a using (authorid)
) x WHERE rn = 1

在不支持窗口功能的RDBMS中（例如MySQL 5.x），使用NOT EXISTS条件可能比聚合更有效：

SELECT
    CONCAT(a.fname, ' ', a.lname),
    b.title,
    ROW_NUMBER() OVER(PARTITION BY authorid ORDER BY pubdate DESC) rn
FROM
    books b
    JOIN bookauthor ba using (isbn)
    JOIN author a using (authorid)
WHERE NOT EXISTS (
    SELECT 1
    FROM books b1 JOIN bookauthor ba1 using (isbn)
    WHERE ba1.authorid = b.authorid AND b1.pubdate > b.pubdate
)

mySQL，查找每位作者写的最新书籍

2 个答案: