將 mysql 讀取到 dataframe 如果有大量資料

要獲取大資料，我們可以在 pandas 中使用生成器並以塊的形式載入資料。

import pandas as pd
from sqlalchemy import create_engine
from sqlalchemy.engine.url import URL

# sqlalchemy engine
engine = create_engine(URL(
    drivername="mysql"
    username="user",
    password="password"
    host="host"
    database="database"
))

conn = engine.connect()

generator_df = pd.read_sql(sql=query,  # mysql query
                           con=conn,
                           chunksize=chunksize)  # size you want to fetch each time

for dataframe in generator_df:
    for row in dataframe:
        pass  # whatever you want to do