在第4列中添加3列(具有avg()值)

import pymysql

# 连接数据库
conn = pymysql.connect(host='localhost', user='root', password='password', database='mydb')

# 创建游标对象
cursor = conn.cursor()

ALTER TABLE table_name ADD COLUMN column1 INT;
ALTER TABLE table_name ADD COLUMN column2 INT;
ALTER TABLE table_name ADD COLUMN column3 INT;

UPDATE table_name SET column1 = (SELECT AVG(column_name) FROM table_name);
UPDATE table_name SET column2 = (SELECT AVG(column_name) FROM table_name);
UPDATE table_name SET column3 = (SELECT AVG(column_name) FROM table_name);

# 提交事务
conn.commit()

# 关闭游标和连接
cursor.close()
conn.close()