python 实现 pymysql 数据库操作方法

一、安装

pip install pymysql

二、连接数据库

• 三种连接数据库的方式

import pymysql

# 方式一
conn = pymysql.connect('localhost', 'root', 'root')

# 方式二
conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='root', db='', charset='utf8')

# 方式三
config = {
'host': '127.0.0.1',
'port': 3306,
'user': 'root',
'passwd': 'root',
'charset': 'utf8'
}
conn = pymysql.connect(**config)

三、创建数据库

• 创建一个test数据库并进入

import pymysql

db = pymysql.connect("localhost", "root", "root", "test")
# 使用 cursor() 方法创建一个游标对象 cursor
cursor = db.cursor()

cursor.execute('DROP DATABASE IF EXISTS test')
cursor.execute('CREATE DATABASE IF NOT EXISTS test')
conn.select_db('test')

四、创建数据表

• 创建一张user表

import pymysql

db = pymysql.connect("localhost", "root", "root", "test")
cursor = db.cursor()

cursor.execute('CREATE TABLE user(id int primary key,name varchar(30))')

五、插入一条数据

import pymysql

db = pymysql.connect("localhost", "root", "root", "test")
cursor = db.cursor()

try:
# 执行SQL语句
sql = 'INSERT INTO user values("％d","％s")' ％(1,"autofelix")
cursor.execute(sql)
# 提交到数据库执行
db.commit()
except:
# 发生错误时回滚
db.rollback()
finally:
# 关闭游标连接
cursor.close()
# 关闭数据库连接
conn.close()

六、插入多条数据

import pymysql

db = pymysql.connect("localhost", "root", "root", "test")
cursor = db.cursor()

try:
# 执行SQL语句
values = [(1, 'autofelix'), (2, '飞兔小哥')]
cursor.executemany('INSERT INTO user values(％s,％s)', values)
# 提交到数据库执行
db.commit()
except:
# 发生错误时回滚
db.rollback()
finally:
# 关闭游标连接
cursor.close()
# 关闭数据库连接
conn.close()

七、数据统计

import pymysql

db = pymysql.connect("localhost", "root", "root", "test")
cursor = db.cursor()

count = cursor.execute('SELECT * FROM user')
# 统计数据总数
print('total records: ％d' ％count)
# 统计字段数
print('total records:', cursor.rowcount)

八、获取表名信息

import pymysql

db = pymysql.connect("localhost", "root", "root", "test")
cursor = db.cursor()

desc = cursor.description
print("％s ％3s" ％ (desc[0][0], desc[1][0]))

九、获取单条数据

• 使用 fetchone 方法获取单条数据

import pymysql

db = pymysql.connect("localhost", "root", "root", "test")
cursor = db.cursor()

# 使用 execute() 方法执行 SQL 查询
cursor.execute("SELECT VERSION()")

# 使用 fetchone() 方法获取单条数据.
data = cursor.fetchone()

print("Database version : ％s " ％ data)

# 关闭数据库连接
db.close()

十、查询多条数据

import pymysql

db = pymysql.connect("localhost", "root", "root", "test")
cursor = db.cursor()

cursor.execute('SELECT * FROM user')

results = cursor.fetchmany(5)
for r in results:
print (r)

十一、查询所有数据

import pymysql

db = pymysql.connect("localhost", "root", "root", "test")
cursor = db.cursor()

cursor.execute('SELECT * FROM user')

results = cursor.fetchall()
for r in results:
print (r)

十二、上下文管理

• 每次都连接关闭很麻烦，使用上下文管理，简化连接过程

import pymysql
import contextlib

# 定义上下文管理器，连接后自动关闭连接
@contextlib.contextmanager
def mysql(host='127.0.0.1', port=3306, user='root', passwd='', db='test',charset='utf8'):
conn = pymysql.connect(host=host, port=port, user=user, passwd=passwd, db=db, charset=charset)
cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
try:
yield cursor
finally:
conn.commit()
cursor.close()
conn.close()

# 执行sql
with mysql() as cursor:
print(cursor)
count = cursor.execute("select * from user")
row_1 = cursor.fetchone()
print row_count, row_1

来源：https://blog.51cto.com/autofelix/5204217