DB2 - row_number 函数 - 需要输出中的第一个分区行

Question

我在 SQL 下尝试过，但它不起作用。

问题：它没有给出第一个分区行。

我正在添加表详细信息和 SQL。这是针对 DB2 数据库的。

Books Table:  
book_id  
rating 
title 
isbn 
publisher_id


WITH cte_books AS (
    SELECT
        publisher_id,
        ROW_NUMBER() OVER (
            PARTITION BY publisher_id 
            ORDER BY rating DESC
        ) row_num,
        book_id, 
        rating,
        title
    FROM 
        books
    WHERE 
        publisher_id IS NOT NULL
)
SELECT 
  * 
FROM 
    cte_books
WHERE 
    row_num >= 1 AND 
    row_num >= 2;

Answer 1

将ROW_NUMBER() 更改为COUNT(1)，删除ORDER BY 并使用WHERE row_num > 1。

Answer 2

WHERE 
    row_num >= 1 AND 
    row_num >= 2;

实际上是row_num >= 2

 WHERE 
         row_num = 1

将返回第一行

编辑： 如果您想为超过 1 行的人提供所有行 - 这是这样做的方法：

WITH cte_books AS (
    SELECT
        publisher_id,
        ROW_NUMBER() OVER (
            PARTITION BY publisher_id 
            ORDER BY rating DESC
        ) row_num,
        book_id, 
        rating,
        title
    FROM 
        books
    WHERE 
        publisher_id IS NOT NULL
)

SELECT * 
  FROM cte_books t 
 WHERE exists (SELECT 1 
                 FROM cte_books 
                WHERE row_num > 1 
                  AND pubisher_id = t.publisher_id)