使用Python连接MySQL

1、连接数据库

import pymysql

#指定数据库地址、用户、密码、端口，使用connect()方法声明一个Mysql连接对象db
db = pymysql.connect(host='localhost',user='root', password='123456', port=3306)

#调用cursor()方法获得Mysql的操作游标，利用游标来执行SQL语句。
cursor = db.cursor()

#直接用execute()方法执行，第一句用于获得Mysql版本，然后调用fetchone()方法获得第一条数据。
cursor.execute('SELECT VERSION()')
data = cursor.fetchone()
print('Database version:', data)

##创建名称为spiders的数据库
cursor.execute("CREATE DATABASE spiders DEFAULT CHARACTER SET utf8")
db.close()

2、创建表

import pymysql

db = pymysql.connect(host='localhost', user='root', password='123456', port=3306, db='spiders')
cursor = db.cursor()

#创建一个名为students的数据表
sql = 'CREATE TABLE IF NOT EXISTS students (id VARCHAR(255) NOT NULL, name VARCHAR(255) NOT NULL, age INT NOT NULL, PRIMARY KEY (id))'
cursor.execute(sql)
db.close()

3、插入数据

import pymysql

#定义数据
id = '20120001'
user = 'Bob'
age = 20

#连接数据库
db = pymysql.connect(host='localhost', user='root', password='123456', port=3306, db='spiders')
cursor = db.cursor()

#使用格式化符%s来插入数据
sql = 'INSERT INTO students(id, name, age) values(%s, %s, %s)'
try:
    cursor.execute(sql, (id, user, age))
    db.commit()
except:
    db.rollback()
db.close()

4、插入数据（字典）

import pymysql

#构造字典
data = {
    'id': '20120001',
    'name': 'Bob',
    'age': 20
}
table = 'students'

#keys的结果是 id,name,age
keys = ', '.join(data.keys())

#values的结果是 %s, %s, %s
values = ', '.join(['%s'] * len(data))

#使用format()方法将表名、字段名和占位符构造出来。
#最终的SQL语句就被动态构造成 INSERT INTO students (id,name,age) VALUES (%s, %s, %s)
sql = 'INSERT INTO {table}({keys}) VALUES ({values})'.format(table=table, keys=keys, values=values)

db = pymysql.connect(host='localhost', user='root', password='123456', port=3306, db='spiders')
cursor = db.cursor()
try:
    if cursor.execute(sql, tuple(data.values())):
        print('Successful')
        db.commit()
except:
    print('Failed')
    db.rollback()
db.close()

5、更新数据

import pymysql

data = {
    'id': '20120001',
    'name': 'Bob',
    'age': 20
}
table = 'students'
keys = ', '.join(data.keys())
values = ', '.join(['%s'] * len(data))

db = pymysql.connect(host='localhost', user='root', password='123456', port=3306, db='spiders')
cursor = db.cursor()

sql = 'UPDATE students SET age = %s WHERE name = %s'
try:
    cursor.execute(sql, (25, 'Bob'))
    db.commit()
except:
    db.rollback()
db.close()

6、更新数据（去重）

import pymysql

data = {
    'id': '20120001',
    'name': 'Bob',
    'age': 21
}

table = 'students'
keys = ', '.join(data.keys())
values = ', '.join(['%s'] * len(data))

db = pymysql.connect(host='localhost', user='root', password='123456', port=3306, db='spiders')
cursor = db.cursor()

#SQL语句 ON DUPLICATE KEY UPDATE表示如果主键已经存在就执行更新操作i
#sql的值为 INSERT INTO students(id, name, age) VALUES (%s, %s, %s) ON DUPLICATE KEY UPDATE
sql = 'INSERT INTO {table}({keys}) VALUES ({values}) ON DUPLICATE KEY UPDATE'.format(table=table, keys=keys,
                                                                                     values=values)
update = ','.join([" {key} = %s".format(key=key) for key in data])

#sql的值更新为INSERT INTO students(id, name, age) VALUES (%s, %s, %s) ON DUPLICATE KEY UPDATE id = %s, name = %s, age = %s
sql += update

try:
    if cursor.execute(sql, tuple(data.values()) * 2):
        print('Successful')
        db.commit()
except:
    print('Failed')
    db.rollback()
db.close()

7、删除数据

import pymysql

table = 'students'
condition = 'age > 20'
db = pymysql.connect(host='localhost', user='root', password='123456', port=3306, db='spiders')
cursor = db.cursor()
sql = 'DELETE FROM  {table} WHERE {condition}'.format(table=table, condition=condition)
try:
    cursor.execute(sql)
    db.commit()
except:
    db.rollback()

db.close()

8、查询数据

import pymysql

sql = 'SELECT * FROM students WHERE age >= 20'
db = pymysql.connect(host='localhost', user='root', password='123456', port=3306, db='spiders')
cursor = db.cursor()
try:
    cursor.execute(sql)
    #输出长度
    print('Count:', cursor.rowcount)
    #获取结果的第一条数据
    data = cursor.fetchall()
    print(data)
except:
    print('Error')
mysql_connect.close()
mysql_cursor.close()

来源：https://blog.csdn.net/weixin_43249821/article/details/99759139