【笔记】2022.5.27 通过pycharm操作MySQL

1. 通过pycharm插入数据

RIGHT Example：

# example01 - 连接MySQL数据库插入数据

# SQL Injection - SQL注射攻击
# 经验：一定不能够使用字符串拼接或者格式化等方式组装动态的SQL，否则就会直面SQL注射攻击。

import pymysql
from pymysql.cursors import Cursor

no = input('请输入部门编号：')
name = input('请输入部门名称：')
location = input('请输入部门地址：')

# 1. 创建连接
conn = pymysql.connect(host='localhost', port=3306,
                       user='guest', password='guest.618',
                       database='hrs', charset='utf8mb4')

try:
    # 2. 获取游标对象
    with conn.cursor() as cursor:   # type: Cursor

        # 3. 通过游标对象执行SQL语句
        affected_rows = cursor.execute(
            'select dno from tb_dept where dno = (%s)',
            (no,)
        )
        if affected_rows == 0:
            affected_rows = cursor.execute(
                'insert into tb_dept (dno, dname, dloc) '
                'values (%s, %s, %s)',
                (no, name, location)
            )
            if affected_rows == 1:
                print('添加部门成功！！！')
        else:
            print('部门已存在')

    # 4. 手动提交(让之前的操作生效)
    conn.commit()

except pymysql.MySQLError as err:
    # 4. 手动回滚(撤销之前的操作)
    conn.rollback()
    print(err)

finally:
    # 5. 关闭连接
    conn.close()

常见错误：

2. 通过pycharm删除数据

RIGHT Example：

# example02 - 连接MySQL数据库删除数据

import pymysql
from pymysql.cursors import Cursor

no = input('请输入部门编号：')

# 1. 创建连接
conn = pymysql.connect(host='localhost', port=3306,
                       user='guest', password='guest.618',
                       database='hrs', charset='utf8mb4')

try:
    # 2. 获取游标对象
    with conn.cursor() as cursor:   # type: Cursor

        # 3. 通过游标对象执行SQL语句
        affected_rows = cursor.execute(
            'select dno from tb_dept where dno = (%s)',
            (no,)
        )
        if affected_rows == 0:
            print('早已删除')

        else:
            affected_rows = cursor.execute(
                'delete from tb_dept where dno = (%s) ',
                (no,)
            )
            if affected_rows == 1:
                print('删除部门成功！！！')

    # 4. 手动提交(让之前的操作生效)
    conn.commit()

except pymysql.MySQLError as err:
    # 4. 手动回滚(撤销之前的操作)
    conn.rollback()
    print(err)

finally:
    # 5. 关闭连接
    conn.close()

3. 通过pycharm更改数据

RIGHT Example：

# example03 - 连接MySQL数据库更改数据

import pymysql
from pymysql.cursors import Cursor

no = input('请输入部门编号：')
name = input('请输入部门名称：')
location = input('请输入部门地址')

# 1. 创建连接
conn = pymysql.connect(host='localhost', port=3306,
                       user='guest', password='guest.618',
                       database='hrs', charset='utf8mb4')

try:
    # 2. 获取游标对象
    with conn.cursor() as cursor:   # type: Cursor

        # 3. 通过游标对象执行SQL语句
        affected_rows = cursor.execute(
            'update tb_dept set dname = %s, dloc = %s where dno = %s',
            (name, location, no)
        )
        if affected_rows == 1:
            print('更新成功')

    # 4. 手动提交(让之前的操作生效)
    conn.commit()

except pymysql.MySQLError as err:
    # 4. 手动回滚(撤销之前的操作)
    conn.rollback()
    print(err)

finally:
    # 5. 关闭连接
    conn.close()

4. 通过pycharm查数据

# example04 - 连接MySQL数据库查数据

import pymysql
import csv
from pymysql.cursors import Cursor, DictCursor

f = open('员工表.csv', 'w', encoding='utf-8', newline='')
writer = csv.writer(f)
writer.writerow(['员工编号', '员工姓名', '员工职位', '员工主管', '员工月薪', '员工奖金', '所属部门编号'])

# 1. 创建连接
conn = pymysql.connect(host='localhost', port=3306,
                       user='guest', password='guest.618',
                       database='hrs', charset='utf8mb4')

try:
    # 2. 获取游标对象
    with conn.cursor() as cursor:   # type: Cursor

        # 3. 通过游标对象执行SQL语句
        affected_rows = cursor.execute(
            'select eno, ename, job, mgr, sal, comm, dno from tb_emp'
        )
        # 4. 通过游标对象抓取数据
        while data := cursor.fetchone():
            writer.writerow(data)

except pymysql.MySQLError as err:
    print(err)

finally:
    # 5. 关闭连接
    conn.close()