Ubuntu下通过python使用MySQL
参考资料
- MySQL Connector/Python Developer Guide
- python_mysql_tutorial
环境
- Ubuntu 20.04
- Python 3.8.10
- MySQL Server 8.0.34
- mysql-connector-python 8.1.0
安装MySQL
pip install mysql-connector-python # 注意，不要安装成 mysql-connector 了
环境测试
注意：
- 千万不能命名为
mysql.py!- 千万不能命名为
mysql.py!- 千万不能命名为
mysql.py!
import mysql.connector
def get_connection():
connection = mysql.connector.connect(host='localhost',
database='python_db',
user='root',
password='root')
return connection
def close_connection(connection):
if connection:
connection.close()
def read_database_version():
try:
connection = get_connection()
cursor = connection.cursor()
cursor.execute("SELECT version();")
db_version = cursor.fetchone()
print("You are connected to MySQL version: ", db_version)
close_connection(connection)
except (Exception, mysql.connector.Error) as error:
print("Error while getting data", error)
print("Question 1: Print Database version")
read_database_version()
MySQL 的连接和关闭
关于下列代码中
**的解释：python中星号的意义
import mysql.connector
from mysql.connector import errorcode
config = {
'user': 'root',
'password': 'root',
'database': 'mydb',
'host': 'localhost',
'raise_on_warnings': True
}
try:
cnx = mysql.connector.connect(**config)
except mysql.connector.Error as err: # if except happen will execute
print("Database operation ERR")
if err.errno == errorcode.ER_ACCESS_DENIED_ERROR:
print("Something is wrong with your user name or password")
elif err.errno == errorcode.ER_BAD_DB_ERROR:
print("Database does not exist")
else:
print(err)
else: # if no except happen will execute
cnx.close()
print("Database operation OK")
finally: # always execute
print("Finish")
MySQL创建数据库
import mysql.connector
conn = mysql.connector.connect(user='root', password='root')
cursor = conn.cursor()
cursor.execute("drop database if exists my_database") # 通过 if exists 防止数据不存在而报错
sql = "create database my_database"
cursor.execute(sql) # 创建数据库
print("List of databases: ")
cursor.execute("show databases") # 执行 SQL 语句
print(cursor.fetchall()) # 获取 MySQL 的输出，有 fetchone() fetchmany() fetchall() 三个接口
conn.close()
MySQL创建表格及数据库
以下表格数据下载：employees database
import mysql.connector
from mysql.connector import errorcode
DB_NAME = 'employees'
TABLES = {}
TABLES['employees'] = (
"create table `employees` ("
" `emp_no` int(11) NOT NULL AUTO_INCREMENT,"
" `birth_date` date NOT NULL,"
" `first_name` varchar(14) NOT NULL,"
" `last_name` varchar(16) NOT NULL,"
" `gender` enum('M', 'F') NOT NULL,"
" `hire_date` date NOT NULL,"
" primary key (`emp_no`)"
") engine=InnoDB")
TABLES['departments'] = (
"create table `departments` ("
" `dept_no` char(4) NOT NULL,"
" `dept_name` varchar(40) NOT NULL,"
" primary key (`dept_no`), unique key `dept_name` (`dept_name`)"
") engine=InnoDB")
TABLES['salaries'] = (
"create table `salaries` ("
" `emp_no` int(11) NOT NULL,"
" `salary` int(11) NOT NULL,"
" `from_date` date NOT NULL,"
" `to_date` date NOT NULL,"
" primary key (`emp_no`, `from_date`), key `emp_no` (`emp_no`),"
" constraint `salaries_ibfk_1` foreign key (`emp_no`) "
" references `employees` (`emp_no`) on delete cascade"
") engine=InnoDB")
TABLES['dept_emp'] = (
"create table `dept_emp` ("
" `emp_no` int(11) NOT NULL,"
" `dept_no` char(4) NOT NULL,"
" `from_date` date NOT NULL,"
" `to_date` date NOT NULL,"
" primary key (`emp_no`, `dept_no`), key `emp_no` (`emp_no`),"
" key `dept_no` (`dept_no`),"
" constraint `dept_emp_ibfk_1` foreign key (`emp_no`) "
" references `employees` (`emp_no`) on delete cascade,"
" constraint `dept_emp_ibfk_2` foreign key (`dept_no`) "
" references `departments` (`dept_no`) on delete cascade"
") engine=InnoDB")
TABLES['dept_manager'] = (
"create table `dept_manager` ("
" `emp_no` int(11) NOT NULL,"
" `dept_no` char(4) NOT NULL,"
" `from_date` date NOT NULL,"
" `to_date` date NOT NULL,"
" primary key (`emp_no`, `dept_no`),"
" key `emp_no` (`emp_no`),"
" key `dept_no` (`dept_no`),"
" constraint `dept_manager_ibfk_1` foreign key (`emp_no`) "
" references `employees` (`emp_no`) on delete cascade,"
" constraint `dept_manager_ibfk_2` foreign key (`dept_no`) "
" references `departments` (`dept_no`) on delete cascade"
") engine=InnoDB")
TABLES['titles'] = (
"create table `titles` ("
" `emp_no` int(11) NOT NULL,"
" `title` varchar(50) NOT NULL,"
" `from_date` date NOT NULL,"
" `to_date` date NOT NULL,"
" primary key (`emp_no`, `title`, `from_date`), key `emp_no` (`emp_no`),"
" constraint `title_ibfk_1` foreign key (`emp_no`)"
" references `employees` (`emp_no`) on delete cascade"
") engine=InnoDB")
def create_database(cursor):
try:
cursor.execute(
"create database {} default character set 'utf8'".format(DB_NAME))
except mysql.connector.Error as err:
print("Failed creating database: {}".format(err))
exit(1)
cnx = mysql.connector.connect(user='root', password='root')
cursor = cnx.cursor()
try:
cursor.execute("USE {}".format(DB_NAME))
except mysql.connector.Error as err:
print("Database {} does not exists.".format(DB_NAME))
if err.errno == errorcode.ER_BAD_DB_ERROR:
create_database(cursor)
print("Database {} created successfully.".format(DB_NAME))
cnx.database = DB_NAME
else:
print(err)
exit(1)
for table_name in TABLES:
table_description = TABLES[table_name]
try:
print("Creating table {}: ".format(table_name), end='')
cursor.execute(table_description)
except mysql.connector.Error as err:
if err.errno == errorcode.ER_TABLE_EXISTS_ERROR:
print("already exist.")
else:
print(err.msg)
else:
print("OK")
cursor.close() # cursor 也需要关闭
cnx.close()
import mysql.connector
conn = mysql.connector.connect(user='root', password='root')
cursor = conn.cursor()
cursor.execute("show databases")
print(cursor.fetchall()) # 获取并打印 MySQL 的输出
cursor.execute("use mydb") # 选择数据库
cursor.execute("drop table if exists employee") # 如果已经存在 employee 表格，则删除
# 除了上面在双引号中添加SQL语句，还可以利用 python 多行字符串的语法，在三引号中添加 SQL 语句，这样就没有这么多的引号，看起来清晰很多
sql = '''
create table employee(
first_name char(20) not null,
last_name char(20),
age int,
sex char(1),
income float
)
'''
cursor.execute(sql) # 新建 employee 表格
cursor.execute("desc employee") # 显示表格详情
print(cursor.fetchall())
cursor.execute("show create table employee") # 显示创建表格的源码！
print(cursor.fetchall())
cursor.close()
conn.close()
插入数据 INSERT INTO
import mysql.connector
conn = mysql.connector.connect(user='root', password='root', database='mydb')
cursor = conn.cursor()
sql = '''
insert into employee(first_name, last_name, age, sex, income) values('Mac', 'Mohan', 20, 'M', 2000)
'''
try:
cursor.execute(sql)
conn.commit()
print("commit")
except:
conn.rollback()
print(rollback)
conn.close()
import mysql.connector
conn = mysql.connector.connect(user='root', password='root', database='mydb')
cursor = conn.cursor()
# 还可以通过这种方式执行 SQL 语句，这样就不需要重复写 SQL 语句了，只需要写需要使用的数据即可
sql = '''
insert into employee(first_name, last_name, age, sex, income) values(%s, %s, %s, %s, %s)
'''
data1 = ('Ramya', 'Ramapriya', 25, 'F', 5000)
data2 = ('shadow3d', 'Denis', 28, 'M', 30000)
try:
cursor.execute(sql, data1)
cursor.execute(sql, data2)
conn.commit()
print("insert OK, commit")
except:
print("insert failed, rollback")
conn.rollback()
conn.close()
查看数据 select
import mysql.connector
conn = mysql.connector.connect(user='root', password='root', database='mydb')
cursor = conn.cursor()
sql = "select * from employee"
# 通过 fetchone() 每次只读一行，可以更直观的显示查询结果
print("read one by one:")
cursor.execute(sql)
result = cursor.fetchone()
while result:
print("\t", result)
result = cursor.fetchone()
# 通过 fetchmany() 指定每次读取的行数
print("\nread two by two:")
cursor.execute(sql)
result = cursor.fetchmany(size=2)
while result:
print("\t", result)
result = cursor.fetchmany(size=2)
conn.close()
错误及原因
ModuleNotFoundError: No module named 'mysql.connector'; 'mysql' is not a package
以上错误是由于将本地的python文件命名成了mysql.py导致，改个名字就好了；mysql.connector.errors.NotSupportedError: Authentication plugin 'caching_sha2_password' is not supported
以上错误是由于安装的模块错了，我们需要安装mysql-connector-python，而安装成了mysql-connector;