Question

我试图展示出发的唯一作者书籍数量最多的I_PUBLISHER，我怎样才能在SQL语句中实现这一点？

情景：

 Publisher A publishes 10 books with 10 unique author
 Publisher B publishes 10 book with that 10 book from same author.

 BOOK_ID, BOOK_TITLE, BOOK_AUTHOR_ID, BOOK_PUBLISHER,

 SQL statement to get the publisher name with largest number of UNIQUE author

Answer 1

尝试

SELECT * 
  FROM
(
  SELECT book_publisher, COUNT(DISTINCT book_author_id) author_count
    FROM table1
   GROUP BY book_publisher
   ORDER BY author_count DESC 
)
 WHERE rownum = 1

或

WITH cte AS
(
  SELECT book_publisher, COUNT(DISTINCT book_author_id) author_count
    FROM table1
   GROUP BY book_publisher
)
SELECT book_publisher
  FROM cte
 WHERE author_count = 
(
  SELECT MAX(author_count) 
    FROM cte
)

或使用分析功能

SELECT book_publisher, author_count 
  FROM
(
  SELECT book_publisher,
         COUNT(DISTINCT book_author_id) author_count,
         DENSE_RANK() OVER (ORDER BY COUNT(DISTINCT book_author_id) DESC) rank
    FROM table1
   GROUP BY book_publisher
)
 WHERE rank = 1

这是 SQLFiddle 演示

如何实现SQL查询，max（count（distinct attribute_name））

1 个答案: