PyMySQL学习笔记

一些常用函数及解释

db = pymysql.connect('host','user','password','database') # 连接数据库

cursor = db.cursor() # 创建游标对象

cursor.execute(sql) # 执行sql语句sql为sql语句

data = cursor.fetchone() # 获取单条数据（具体用法见下面示例）

data_list = fetchall() # 接收全部的返回结果行

db.commit() # 提交到数据库执行

db.rollback() # 发生错误回滚

db.close() # 关闭连接

主要操作是通过sql语句递交给execute()函数执行

以下是一些常用方法的例子

数据库创建表操作代码示例

import pymysql

# 链接数据库
db = pymysql.connect("yourhost", "yourname", "yourpassword", "yourdatabase")

# 创建游标对象
cursor = db.cursor()

# 使用execute()方法执行SQL，如果表存在则删除
cursor.execute("DROP TABLE IF EXISTS EMPLOYEE")

# SQL语句创建表
sql = """
        CREATE TABLE EMPLOYEE (
        FIRST_NAME CHAR(20) NOT NULL,
        LAST_NAME CHAR(20),
        AGE INT,
        SEX CHAR(1),
        INCOME FLOAT )
        """
cursor.execute(sql)

# 关闭数据库连接
db.close()

数据库插入操作代码示例

import pymysql

config = {
    "host":"yourhost",
    "user":"yourname",
    "password":"yourpassword",
    "database":"yourdatabase"
}

db = pymysql.connect(**config)

cursor = db.cursor()
F_name = 'Dawei'
L_name = 'Wang'
age = 20
sex = 'M'
income = 2000

# 注意 %s 外加引号，作为字符，否者mysql会认为是一个column
sql = "INSERT INTO EMPLOYEE (FIRST_NAME, 
       LAST_NAME, AGE, SEX, INCOME) VALUES 
       ('%s', '%s',  '%s',  '%s',  '%s')" %
       (F_name, L_name, age, sex, income)
try:
    # 执行SQL语句
    cursor.execute(sql)
    # 提交到数据库执行，为了及时跟进数据库这句最好加上
    db.commit()
except:
    # 如果发生错误则回滚
    db.rollback()

db.close()

数据库查询操作代码示例

import pymysql

config = {
    "host":"yourhost",
    "user":"yourname",
    "password":"yourpassword",
    "database":"yourdatabase"
}

db = pymysql.connect(**config)

cursor = db.cursor()

# SQL 查询语句
sql = "SELECT * FROM EMPLOYEE 
       WHERE INCOME > %s" % (1000)

try:
    # 执行语句
    cursor.execute(sql)
    # 获取所有列表记录
    results = cursor.fetchall()
    for row in results:
        fname = row[0]
        lname = row[1]
        age = row[2]
        sex = row[3]
        income = row[4]
        # 打印结果
        print("fname = %s, lname = %s, age = %s, sex = %s, income = %s" % 
             (fname, lname, age, sex, income ))
except:
    print("Error: unable to fetch data")

db.close()

数据库更新操作代码示例

import pymysql

config = {
    "host":"yourhost",
    "user":"yourname",
    "password":"yourpassword",
    "database":"yourdatabase"
}

db = pymysql.connect(**config)

cursor = db.cursor()

# SQL 更新语句
sql = "UPDATE EMPLOYEE SET AGE = AGE + 1 WHERE SEX = '%c'" % ('M')
try:
    # 执行SQL语句
    cursor.execute(sql)
    db.commit()
except:
    db.rollback()

db.close()

数据库删除操作代码示例

import pymysql

config = {
    "host":"yourhost",
    "user":"yourname",
    "password":"yourpassword",
    "database":"yourdatabase"
}

db = pymysql.connect(**config)

cursor = db.cursor()

# SQL 删除语句
sql = "DELETE FROM EMPLOYEE WHERE AGE > %s" % (20)

try:
    cursor.execute(sql)
    db.commit()
except:
    db.rollback()

db.close()