# -*- encoding: utf-8 -*-
'''
@File    :   creat_student.py   
@License :   (C)Copyright 2018-2022

@Modify Time      @Author    @Version    @Desciption
------------      -------    --------    -----------
2023/4/16 18:51   zart20      1.0         None
'''
import pymysql


def connect_db():
    """链接数据库 """
    db = pymysql.connect(host="127.0.0.1", port=3306, user='root', password="123123", charset="utf8",database="example")  # 链接数据库
    return db

def close_db(db:pymysql.connect):
    """关闭数据库链接"""
    db.close()

def create_table(db:pymysql.connect):
    """创建表"""
    cursor = db.cursor()    # 创建游标
    cursor.execute("DROP TABLE IF EXISTS student;")     # 如果存在student表先删除
    sql = """CREATE TABLE Student (
                                ID CHAR(10) NOT NULL,
                                Name VARCHAR(20),
                                Grade INT 
                                );"""       # 构建创建表结构的SQL语句
    cursor.execute(sql)     # 通过游标执行语句
    cursor.close()      # 关闭游标


def insert_table(db:pymysql.connect):
    """插入数据"""
    cursor = db.cursor()
    sql = """INSERT INTO Student VALUES ('001', 'CZQ', 70),('002', 'LHQ', 80),('003', 'MQ', 90), 
                ('004', 'WH', 80),  ('005', 'HP', 70),('006', 'YF', 66),('007', 'TEST', 100);"""
    try:
        cursor.execute(sql)
        db.commit()     # 插入操作必须提交事务才能成功
        cursor.close()
    except:
        db.rollback()   # 发生错误时回滚
        cursor.close()


def query_table(db:pymysql.connect):
    """查询表"""
    cursor = db.cursor()
    sql = """SELECT * FROM student"""
    try:
        cursor.execute(sql)
        results = cursor.fetchall()     # 获取所有记录列表
        for row in results:     # 遍历所有表记录
            print(row)          # 打印输出
        cursor.close()
    except:
        db.rollback()   # 发生错误时回滚
        cursor.close()


def delete_db(db:pymysql.connect):
    """删除数据 """
    cursor = db.cursor()
    sql = "DELETE FROM Student WHERE Grade = %d;"% 100
    print(sql)
    try:
        cursor.execute(sql)
        db.commit()
        cursor.close()
    except Exception as e:
        print(e)
        db.rollback()
        cursor.close()


def update_db(db:pymysql.connect):
    """更新数据"""
    cursor = db.cursor()
    sql = "UPDATE Student SET Grade = Grade + 3 WHERE ID = '%s';" % '003'
    print(sql)
    try:
        cursor.execute(sql)
        db.commit()
        cursor.close()
    except Exception as e:
        print(e)
        db.rollback()
        cursor.close()



if __name__ == '__main__':
    db = connect_db()   # 链接数据库
    query_table(db)     # 查询表
    update_db(db)       # 修改记录
    query_table(db)     # 查询表
    # close_db(db)        # 关闭数据库链接释放资源




    # create_table(db)    # 创建表
    # insert_table(db)    # 插入数据
    # # delete_db(db)
    # #
    # # update_db(db)
    #
    # # 检查数据库的变化
    # cursor2 = db.cursor()
    # cursor2.execute("show tables;")  # 显示所有表
    # print(cursor2.fetchall())
    # cursor2.execute("DESCRIBE student;")  # 查看表结构
    # print(cursor2.fetchall())
    #
    # cursor2.execute("SELECT * FROM student;")  # 查看student表所有记录
    # print(cursor2.fetchall())


    # cursor2.close()
    # db.close()  # 关闭链接