将存储过程转换为 python pandas 代码？答案

【问题标题】：Convert stored procedure to python pandas code?将存储过程转换为 python pandas 代码？
【发布时间】：2021-04-20 09:11:50
【问题描述】：

要创建的列使用列作者类型进行排名。

例子：

PMID	Rank
200	3
201	0
200	0
202	0
200	2
201	1
200	1

预期：

PMID	Rank	Author_type
200	3	Last Author
201	0	First Author
200	0	First Author
202	0	First Author
200	2	Co Author
201	1	Last Author
200	1	Co Author

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

ALTER PROCEDURE [datacleaning].[pub_set_authors]
AS
BEGIN
    WITH cte AS 
    (
        SELECT 
            *,
            ROW_NUMBER() OVER (PARTITION BY [pub_id] ORDER BY [rank] DESC) AS rnk
        FROM 
            datacleaning.pubmed_details
    )
    UPDATE datacleaning.pubmed_details
    SET author_type = 'Last Author'
    WHERE row_id IN (SELECT row_id
                     FROM cte
                     WHERE rnk = 1)

    UPDATE datacleaning.pubmed_details
    SET author_type = 'First Author'
    WHERE rank = 0;

    UPDATE datacleaning.pubmed_details
    SET author_type = 'Co Author'
    WHERE author_type is NULL;
END

【问题讨论】：

标签： python sql pandas dataframe

【解决方案1】：

这样就得到了上面的结果；要复制 sql 代码中的 row_number over partition 部分，您可以将 groupby 与 cumcount 结合使用。下一步使用np.select，类似于多个case-when表达式：

(df.assign(row_number = df.groupby("PMID").Rank.cumcount(), 
           Author_type = lambda df: np.select([df.Rank == 0, 
                                               df.row_number.isin([0, 1]),  
                                               df.row_number > 1], 
                                              ['First Author', 
                                               'Last Author', 
                                               'Co Author'])
            )
  .drop(columns = 'row_number')
)



   PMID  Rank   Author_type
0   200     3   Last Author
1   201     0  First Author
2   200     0  First Author
3   202     0  First Author
4   200     2     Co Author
5   201     1   Last Author
6   200     1     Co Author

【讨论】：