如何在数据表中将列值转换为新列？

SELECT
  employee_id,
  salary,
  CASE
    WHEN salary < 50000 THEN 'Low'
    WHEN salary >= 50000 AND salary < 100000 THEN 'Medium'
    ELSE 'High'
  END AS salary_level
FROM
  employees;

import pandas as pd

# 读取数据表
df = pd.read_csv('employees.csv')

# 定义转换函数
def convert_salary_level(salary):
    if salary < 50000:
        return 'Low'
    elif salary >= 50000 and salary < 100000:
        return 'Medium'
    else:
        return 'High'

# 使用apply方法将转换函数应用于原始列，并赋予新列
df['salary_level'] = df['salary'].apply(convert_salary_level)

# 打印转换后的数据表
print(df)