1、加载库、定义函数
import pandas as pd import pymysql def mycursor(db_name=None): '''连接数据库，创建游标''' config = dict(zip(['host', 'user', 'port', 'password'], ['192.168.137.155', 'shanger', 3306, '0123'])) config.update(database=db_name) connection = pymysql.connect(**config) cursor = connection.cursor() return cursor def use(db_name): '''切换数据库，返回游标''' return mycursor(db_name) def query(sql): '''以数据框形式返回查询据结果''' cursor.execute(sql) data = cursor.fetchall() # 以元组形式返回查询数据 header = [t[0] for t in cursor.description] df = pd.DataFrame(list(data), columns=header) # pd.DataFrem 对列表具有更好的兼容性 return df def select_all_from(table): sql = f'select * from {table};' return query(sql)
2、统计
cursor = use('sql123') # 切换数据库
select_all_from('poptbl') # 查看所有记录
分组统计
sql = ''' select case pref_name when '德岛' then '四国' when '香川' then '四国' when '爱媛' then '四国' when '高知' then '四国' when '福冈' then '九州' when '佐贺' then '九州' when '长崎' then '九州' else '其他' end as 地区, sum(population) as 人口数 from poptbl group by 1; ''' query(sql).sort_values(by='人口数', ascending=False)
