python操作mysql数据库

一、理论

通过python的模块来连接数据库，实现对数据的增删改查。

二、实践

实验环境
101	mysql
102	python

过程
101
[root@localhost ~]# ls
anaconda-ks.cfg  init.sql  mysql-8.0.36-linux-glibc2.28-x86_64.tar.xz
mysql> source init.sql
Query OK, 1 row affected (0.01 sec)

Database changed
Query OK, 0 rows affected (0.05 sec)

Query OK, 0 rows affected (0.06 sec)

Query OK, 4 rows affected (0.16 sec)
Records: 4  Duplicates: 0  Warnings: 0

Query OK, 4 rows affected (0.01 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| testdb             |
+--------------------+
5 rows in set (0.00 sec)


mysql> create user 'root'@'%' identified by 'sooo123';
Query OK, 0 rows affected (0.04 sec)

mysql> grant all on *.* to 'root'@'%';
Query OK, 0 rows affected (0.01 sec)

mysql> alter user 'root'@'%' identified with mysql_native_password by 'sooo123'
    -> ;


102

[root@localhost ~]# dnf -y install mysql
[root@localhost ~]# mysql -uroot -psooo123 -h192.168.10.101
mysql> exit
Bye


[root@localhost ~]# pip install mysql-connector-python  # 安装模块来连接mysql
Looking in indexes: http://mirrors.aliyun.com/pypi/simple
Collecting mysql-connector-python
  Downloading http://mirrors.aliyun.com/pypi/packages/b9/38/96a602ad402fb71175d83bed3178bd8c16e04251d279e314e0bc53e0b861/mysql_connector_python-9.3.0-cp311-cp311-manylinux_2_28_x86_64.whl (33.9 MB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 33.9/33.9 MB 5.1 MB/s eta 0:00:00
Installing collected packages: mysql-connector-python
Successfully installed mysql-connector-python-9.3.0

[root@localhost ~]# pip install pymysql	# 安装pymysql也可以连接mysql
Looking in indexes: http://mirrors.aliyun.com/pypi/simple
Collecting pymysql
  Downloading http://mirrors.aliyun.com/pypi/packages/0c/94/e4181a1f6286f545507528c78016e00065ea913276888db2262507693ce5/PyMySQL-1.1.1-py3-none-any.whl (44 kB)
Installing collected packages: pymysql
Successfully installed pymysql-1.1.1


[root@localhost ~]# vim q.py 
import pymysql

db=pymysql.connect(
        host="192.168.10.101",
        user="root",
        password="sooo123",
        database="testdb"
        )

cursor=db.cursor()  # 创建游标对象

cursor.execute("select * from users")  # 执行sql语句

results=cursor.fetchall()  # 获取查询结果，fetchall()用于获取所有结果。
for row in results:  # row为变量 results为取值列表，遍历输出。
    print(row)

# 关闭游标连接和数据库连接
cursor.close()
db.close()


[root@localhost ~]# python3 q.py 
(1, 'Alice', 25)
(2, 'Bob', 30)
(3, 'Charlie', 35)
(4, 'David', 28)



[root@localhost ~]# vim q.py 
import pymysql

db=pymysql.connect(
        host="192.168.10.101",
        user="root",
        password="sooo123",
        database="testdb"
        )

cursor=db.cursor()  # 创建游标对象

cursor.execute("insert into users(name,age) values(%s,%s)",("Alice",25)) # %s是占
位符，用后面的数值来替换。

cursor.execute("select * from users")  # 执行sql语句

results=cursor.fetchall()  # 获取查询结果，fetchall()用于获取所有结果。
for row in results:  # row为变量 results为取值列表，遍历输出。
    print(row)

# 关闭游标连接和数据库连接
cursor.close()
db.close()


[root@localhost ~]# python3 q.py 
(1, 'Alice', 25)
(2, 'Bob', 30)
(3, 'Charlie', 35)
(4, 'David', 28)
(5, 'Alice', 25)

[root@localhost ~]# vim q.py
import pymysql

db=pymysql.connect(
        host="192.168.10.101",
        user="root",
        password="sooo123",
        database="testdb"
        )

cursor=db.cursor()  # 创建游标对象

cursor.execute("update users set age=%s where name=%s",(26,"Alice")) # %s是占位符，用后面的数值来替换。
db.commit() # 提交事务，保存更新的数据。

cursor.execute("select * from users")  # 执行sql语句

results=cursor.fetchall()  # 获取查询结果，fetchall()用于获取所有结果。
for row in results:  # row为变量 results为取值列表，遍历输出。
    print(row)

# 关闭游标连接和数据库连接
cursor.close()
db.close()

[root@localhost ~]# python3 q.py 
(1, 'Alice', 26)
(2, 'Bob', 30)
(3, 'Charlie', 35)
(4, 'David', 28)

[root@localhost ~]# vim q.py
import pymysql

db=pymysql.connect(
        host="192.168.10.101",
        user="root",
        password="sooo123",
        database="testdb"
        )

cursor=db.cursor()  # 创建游标对象

cursor.execute("delete from users where name=%s",("Alice",))
db.commit() # 提交事务，保存更新的数据。

cursor.execute("select * from users")  # 执行sql语句

results=cursor.fetchall()  # 获取查询结果，fetchall()用于获取所有结果。
for row in results:  # row为变量 results为取值列表，遍历输出。
    print(row)

# 关闭游标连接和数据库连接
cursor.close()
db.close()

[root@localhost ~]# python3 q.py 
(2, 'Bob', 30)
(3, 'Charlie', 35)
(4, 'David', 28)

[root@localhost ~]# vim q.py
import pymysql

db=pymysql.connect(
        host="192.168.10.101",
        user="root",
        password="sooo123",
        database="testdb"
        )

cursor=db.cursor()  # 创建游标对象

 使用executemany()方法一次执行多条sql语句。
cursor.executemany(
        "insert into users(name,age) values(%s,%s)",
        [("Bob",30),("Charlie",35),("David",28)]
        )
db.commit() # 提交事务，保存更新的数据。

cursor.execute("select * from users")  # 执行sql语句

results=cursor.fetchall()  # 获取查询结果，fetchall()用于获取所有结果。
for row in results:  # row为变量 results为取值列表，遍历输出。
    print(row)

# 关闭游标连接和数据库连接
cursor.close()
db.close()
[root@localhost ~]# python3 q.py 
(2, 'Bob', 30)
(3, 'Charlie', 35)
(4, 'David', 28)
(6, 'Bob', 30)
(7, 'Charlie', 35)
(8, 'David', 28)


[root@localhost ~]# vim q.py 
import pymysql

db=pymysql.connect(
        host="192.168.10.101",
        user="root",
        password="sooo123",
        database="testdb"
        )

cursor=db.cursor()  # 创建游标对象


cursor.execute("select * from users where name like %s",("%a%",))
db.commit() # 提交事务，保存更新的数据。


#cursor.execute("select * from users")  # 执行sql语句

results=cursor.fetchall()  # 获取查询结果，fetchall()用于获取所有结果。
for row in results:  # row为变量 results为取值列表，遍历输出。
    print(row)

# 关闭游标连接和数据库连接
cursor.close()
db.close()

[root@localhost ~]# python3 q.py 
(3, 'Charlie', 35)
(4, 'David', 28)
(7, 'Charlie', 35)
(8, 'David', 28)

[root@localhost ~]# vim q.py 
import pymysql

db=pymysql.connect(
        host="192.168.10.101",
        user="root",
        password="sooo123",
        database="testdb"
        )

cursor=db.cursor()  # 创建游标对象

 内连接查询。
cursor.execute("""
               select users.name,orders.amount
               from users
               inner join orders on users.id=orders.user_id
               """)

results=cursor.fetchall()  # 获取查询结果，fetchall()用于获取所有结果。
for row in results:  # row为变量 results为取值列表，遍历输出。
    print(row)

# 关闭游标连接和数据库连接
cursor.close()
db.close()


[root@localhost ~]# python3 q.py
('Bob', Decimal('150.75'))
('Charlie', Decimal('200.00'))



使用连接池
安装库
[root@localhost ~]# pip3 install dbutils
Successfully installed dbutils-3.1.0


[root@localhost ~]# vim b.py
from dbutils.pooled_db import PooledDB
import pymysql

# 数据库连接配置
dbconfig={
        "host":"192.168.10.101",
        "user":"root",
        "password":"sooo123",
        "database":"testdb"
        }
# 创建连接池
connection_pool=PooledDB(
        creator=pymysql,  # 使用pymysql作为数据库连接库。
        maxconnections=5, # 连接池中最大连接数。
        **dbconfig    # dbconfig是前面定义的字典，**表示引用字典，将字典中的键值对解包为独立的关键字参数。
        )

# 从连接池中获取连接时，可用connection()方法。每次获取到的连接都可以直接执行数据>库操作。
db_connection=connection_pool.connection()
cursor=db_connection.cursor()

cursor.execute("select * from users")
results=cursor.fetchall()

for row in results:
    print(row)
    

cursor.close()

db_connection.close()  # 关闭连接池，连接会自动归还给连接池

[root@localhost ~]# python3 b.py
(2, 'Bob', 30)
(3, 'Charlie', 35)
(4, 'David', 28)
(6, 'Bob', 30)
(7, 'Charlie', 35)
(8, 'David', 28)

[root@localhost ~]# vim c.py


事务
[root@localhost ~]# vim c.py
import pymysql

# 连接到数据库
conn=pymysql.connect(
        host="192.168.10.101",
        user="root",
        password="sooo123",
        database="testdb"
        )

cursor=conn.cursor()

conn.autocommit=False

try:
    # 开始事务
    cursor.execute("start transaction")

    # 执行插入操作
    cursor.execute("insert into users(name,age) values('Eve',22)")
    cursor.execute("insert into orders (user_id,amount) values((select id from users where name='Eve'),120.50)")

    # 提交事务
    conn.commit()
    print("事务已提交.")

except pymysql.MySQLError as err:
    # 如果发生错误，回滚事务
    print (f"错误：{err}")
    conn.rollback()
    print ("事务已回滚。")

finally:
           # 关闭游标和连接
           cursor.close()



[root@localhost ~]# python3 c.py
事务已提交.


[root@localhost ~]# vim d.py
import pymysql

# 连接到数据库
conn=pymysql.connect(
        host="192.168.10.101",
        user="root",
        password="sooo123",
        database="testdb"
        )

cursor=conn.cursor()

cursor.execute("select * from users")
#cursor.execue("select * from orders")

aaa=cursor.fetchall()
for row in aaa:
    print(row)


cursor.close()
conn.close()

[root@localhost ~]# python3 d.py
(2, 'Bob', 30)
(3, 'Charlie', 35)
(4, 'David', 28)
(6, 'Bob', 30)
(7, 'Charlie', 35)
(8, 'David', 28)
(9, 'Eve', 22)


[root@localhost ~]# vim d.py
import pymysql

# 连接到数据库
conn=pymysql.connect(
        host="192.168.10.101",
        user="root",
        password="sooo123",
        database="testdb"
        )

cursor=conn.cursor()

#cursor.execute("select * from users")
cursor.execute("select * from orders")

aaa=cursor.fetchall()
for row in aaa:
    print(row)


cursor.close()
conn.close()

[root@localhost ~]# python3 c.py
(2, 2, Decimal('150.75'), datetime.datetime(2025, 4, 21, 9, 25, 54))
(3, 3, Decimal('200.00'), datetime.datetime(2025, 4, 21, 9, 25, 54))
(5, 9, Decimal('120.50'), datetime.datetime(2025, 5, 25, 20, 35, 36))