PyMysql

Posted 2020-11-01 xuerh

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Pymysql介绍
PyMySQL 是在 Python3.x 版本中用于连接 MySQL 服务器的一个库，Python2中则使用mysqldb。
Django中也可以使用PyMySQL连接MySQL数据库。

基本使用
# 导入pymysql模块
import pymysql
# 连接database
conn = pymysql.connect(host=“你的数据库地址”, user=“用户名”,password=“密码”,
                                        database=“数据库名”,charset=“utf8”)
# 得到一个可以执行SQL语句的光标对象
cursor = conn.cursor()
# 定义要执行的SQL语句
sql =CREATE TABLE USER1 (
            id INT auto_increment PRIMARY KEY ,
            name CHAR(10) NOT NULL UNIQUE,
            age TINYINT NOT NULL
            )ENGINE=innodb DEFAULT CHARSET=utf8;

# 执行SQL语句
cursor.execute(sql)
# 关闭光标对象
cursor.close()
# 关闭数据库连接
conn.close()

返回字典格式的数据
conn = pymysql.connect(
    host="127.0.0.1", port=3306, user="root",
    password="123456", database="task", charset="utf8")
cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
cursor.execute("select * from goods;")
ret2 = cursor.fetchall()
print("=" * 100)
cursor.close()
conn.close()
print(ret2)

注意：
charset=“utf8”，编码不要写成"utf-8"


二 . 增删改查 操作

1 . 增  加 插入数据失败回滚
conn = pymysql.connect(host="127.0.0.1",port=3306, user="root", password="123456",database="task",charset="utf8")
cursor = conn.cursor()
sql = "insert into tb2(name, age) values(%s, %s);"

name = "小刚"
age = 22
try:
    cursor.execute(sql, [name, age])
    conn.commit()
except Exception as e:
    conn.rollback()
    print(e)
cursor.close()
conn.close()



     批量操作 （注意是cursor.executemany)
     
conn = pymysql.connect(host="127.0.0.1",port=3306, user="root", password="123456",database="task",charset="utf8")
cursor = conn.cursor()
sql = "insert into tb2(name, age) values(%s, %s);"
data = [
    ("ahuango",6),
    ("ahoongi",7),
]
try:
    cursor.executemany(sql, data)
    conn.commit()
except Exception as e:
    conn.rollback()
    print(e)
cursor.close()
conn.close()


       获取插入数据的ID(关联操作时会用到)

conn = pymysql.connect(host="127.0.0.1",port=3306, user="root", password="123456",database="task",charset="utf8")
cursor = conn.cursor()
sql = "insert into tb2(name, age) values(%s, %s);"

name = "小刚2"
age = 20
try:
    cursor.execute(sql, [name, age])
    conn.commit()

    #  获取刚插入数据的 id
    last_id = cursor.lastrowid
    print(last_id)
except Exception as e:
    conn.rollback()
    print(e)
cursor.close()
conn.close()


             删除数据
conn = pymysql.connect(host="127.0.0.1",port=3306, user="root", password="123456",database="task",charset="utf8")
cursor = conn.cursor()
sql = "delete from tb2 where id=%s;"

try:
    cursor.executemany(sql, [10])
    conn.commit()
except Exception as e:
    conn.rollback()
    print(e)
cursor.close()
conn.close()



        修改数据
conn = pymysql.connect(host="127.0.0.1",port=3306, user="root", password="123456",database="task",charset="utf8")
cursor = conn.cursor()
sql = "update tb2 set age=%s where id=%s;"

age = 88
id = 12
try:
    cursor.execute(sql, [age, id])
    conn.commit()
except Exception as e:
    conn.rollback()
    print(e)
cursor.close()
conn.close()


            最重要的查看数据
conn = pymysql.connect(host="127.0.0.1", port=3306, user="root", password="123456", database="task", charset="utf8")
cursor = conn.cursor()
sql = "select * from tb2;"

cursor.execute(sql)
ret1 = cursor.fetchone() #取一条
ret2 = cursor.fetchall() #取全部的数据
cursor.close()
conn.close()
print(ret1)
print(ret2)  #返回元组 形式
  
  
       进阶用法
       
# 可以获取指定数量的数据
cursor.fetchmany(3)
# 光标按绝对位置移动1
cursor.scroll(1, mode="absolute")
# 光标按照相对位置(当前位置)移动1
cursor.scroll(1, mode="relative")