替換mysql python中的列值的邏輯

Question

+--- -----+------------+-------------+
|master_id| product_id |products     |
+---------+------------+-------------+
| 0       | 123       | home        |
| 12      | 234       | office      |
| 15      | 456       | home        |
| 0       | 678       | office      |
| 25      | 890       | home        |
| 0       | 145       | office      |
+---+-----------------+--------------+

我有這個表（只顯示一部分行，超過1000行），我想寫一個邏輯，這樣，每當

master_id = 0，master_id = product_id

我將其移入了熊貓數據框。 現在我該怎么寫這個邏輯

Answer 1

這是你想要的嗎？

select (case when master_id = 0 then product_id else master_id end) as master_id,
       product_id, products
from t;

Answer 2

您不需要熊貓，您可以直接通過數據庫進行操作。

如果您只想以不同的方式顯示記錄：

SELECT CASE master_id WHEN 0 THEN product_id ELSE master_id END AS master_id,
       product_id,
       products
FROM   mytable

如果您實際上要更新數據庫，則更加簡單：

UPDATE mytable
SET    master_id = product_id
WHERE  master_id = 0

Answer 3

如果要使用熊貓數據框，則可以使用numpy.where函數

import numpy as np
import pandas as pd

# initialise dataframe
df = pd.DataFrame([[0, 12, 15, 0, 25],
                  [123, 234, 456, 678, 890],
                  ['home', 'office', 'home', 'office', 'home']]).T
df.columns = ['master_id', 'product_id', 'products']

# Now do fix master_id
df.master_id = np.where(df.master_id == 0, df.product_id, df.master_id)

# New df:
    master_id   product_id  products
0   123          123          home
1   12           234          office
2   15           456          home
3   678          678          office
4   25           890          home