python讀寫mysql數據庫

方法一：

1. python連接mysql數據庫：需要用到 pymysql 庫和 sqlalchemy庫：

import pandas as pd
from sqlalchemy import create_engine
import pymysql

創建連接 create_engine：

con_engine = create_engine('mysql+pymysql://username:passwd@localhost:3306/database_name')
# 示例：
# con_engine = create_engine('mysql+pymysql://root:123456@localhost:3306/database_name') 
# username：數據庫用戶名，例如 root
# passwd：密碼，例如 123456
# localhost：host主機地址，例如：127.0.0.1 
# 3306：是數據庫的端口，一般是3306，但是也可能改變
# database_name：數據庫名 
con_engine = create_engine('mysql+pymysql://username:passwd@localhost:3306/database_name?charset=utf8') #需要時也可用

2. 提供 sql 語句

sql_ = "select * from table_name;" #table_name某個表名

3. 執行查詢，使用 read_sql_query 得到pandas的dataframe數據

df_data = pd.read_sql_query(sql_, con_engine)
xxx = df['key_words'].tolist()
print(xxx)

4. 寫數據到 mysql 數據庫

#寫兩列數據，建立dataframe格式數據
df_write = pd.DataFrame({'id_py':[1,2,3,4],'name_py':['Tom','Bob','Cathy','Jack']})
df_write.to_sql('table_py', con_engine, index = False) # index = False表示不加索引列，寫到table_py表，如果表已經存在，會報錯：ValueError: Table 'table_py' already exists.

 

方法二：使用 read_sql

# username = 'root'
# passwd = '123456'
# database_name = 'db_test'
con_engine = pymysql.connect(host = 'localhost' ,user = username, password = passwd, database = database_name, port=3306, charset = 'utf8') #通過參數形式傳遞，參數是字符串形式
sql_ = "select * from table_name;" #table_name某個表名
df_data = pd.read_sql(sql_ , con_engine)

 

方法三：直接使用pymysql進行查詢，插入數據、更新數據、刪除數據等修改數據表的操作需要添加 commit 和 rollback 語句

import pymysql

# 建立數據庫連接，username, passwd, database_name都是如上，預先定義的參數，localhost也可以替換成某個數據庫的ip地址
con_engine = pymysql.connect(host = 'localhost' ,user = username, password = passwd, database = database_name, port=3306, charset = 'utf8')
 
# 使用cursor()方法獲取游標 
cursor = con_engine.cursor()
 
# SQL語句
sql_ = "select * from table_name;"
try:
   # 執行SQL語句
   cursor.execute(sql_)
   # fetchall()獲取所有記錄，形成的是元組，results = cursor.fetchmany(10)獲取前10條，results = cursor.fetchone()獲取一條數據
   results = cursor.fetchall() 
   for row in results:  #依次獲取每一行數據
      id_ = row[0]  #第1列
      key_words_ = row[1]
      type_words_ = row[2]
      address_name_ = row[3]
      # 打印結果
      print(id_,key_words_,type_words_,address_name_)
except:
   print ("Error: unable to fetch data")
 
# 關閉數據庫連接
con_engine.close()

例如刪除操作：

import pymysql

# 建立數據庫連接，username, passwd, database_name都是如上，預先定義的參數，localhost也可以替換成某個數據庫的ip地址
con_engine = pymysql.connect(host = 'localhost' ,user = username, password = passwd, database = database_name, port=3306, charset = 'utf8')
 
# 使用cursor()方法獲取游標 
cursor = con_engine.cursor()
 
# SQL語句
sql_ = "delete * from table_name where id > 5;"
try:
   # 執行SQL語句
   cursor.execute(sql_)
   con_engine.commit()    #提交修改，類似github的commit操作
except:
   con_engine.rollback()  #不成功則回滾
 
# 關閉數據庫連接
con_engine.close()

 

參考：

https://www.jianshu.com/p/238a13995b2b

https://blog.csdn.net/luoluopan/article/details/100074959

https://www.runoob.com/python3/python3-mysql.html