如何将多个大小相同的pandas数据帧组合成一个内聚的数据库？

import pandas as pd
from sqlalchemy import create_engine

engine = create_engine('sqlite:///mydatabase.db')

df1.to_sql('table1', engine, if_exists='replace')
df2.to_sql('table2', engine, if_exists='replace')
df3.to_sql('table3', engine, if_exists='replace')

query = "SELECT * FROM table1 UNION ALL SELECT * FROM table2 UNION ALL SELECT * FROM table3"
df_combined = pd.read_sql_query(query, engine)

with engine.connect() as con:
    con.execute("DROP TABLE table1")
    con.execute("DROP TABLE table2")
    con.execute("DROP TABLE table3")