如何根据列值行绑定重复的列？

-- 错误示例
SELECT product_id, SUM(sales_amount)
FROM sales
GROUP BY product_id;

-- 正确示例
SELECT product_id, category, SUM(sales_amount)
FROM sales
GROUP BY product_id, category;

-- 错误示例
SELECT date, SUM(sales_amount)
FROM sales
GROUP BY date;

-- 如果date列中有重复值，可以考虑添加更多列来唯一标识每条记录
SELECT date, product_id, SUM(sales_amount)
FROM sales
GROUP BY date, product_id;

SELECT date, SUM(sales_amount)
FROM sales
GROUP BY date
ORDER BY date;

import pandas as pd

# 创建示例数据
data = {
    'date': ['2023-01-01', '2023-01-01', '2023-01-02', '2023-01-02'],
    'product_id': [1, 2, 1, 2],
    'sales_amount': [100, 200, 150, 250]
}
df = pd.DataFrame(data)

# 按日期和产品ID分组，并计算总销售额
grouped_df = df.groupby(['date', 'product_id']).agg({'sales_amount': 'sum'}).reset_index()

print(grouped_df)