25.4.14

testdb.sql

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+CREATE DATABASE TESTDB;
+USE TESTDB;
+CREATE TABLE EMPLOYEE (
+    FIRST_NAME CHAR(20) NOT NULL,
+        LAST_NAME CHAR(20),
+        AGE INT,
+        SEX CHAR(1),
+        INCOME FLOAT
+);

作业2.py

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+import pymysql
+# 定义 数据库工具类
+class DBTools(object):
+    # 创建连接 - 类方法。可以直接使用类名调用！
+    @classmethod
+    def __create_conn(cls):
+        conn = pymysql.connect(host="172.16.28.4", port=3306, user="root", password="root", database="books", charset="utf8")
+        # 不能遗漏
+        return conn
+
+    # 查一条记录 - 封装为类方法，方便调用
+    @classmethod
+    def query_one(cls, sql):
+        my_conn = None
+        my_cursor = None
+        res = None
+        try:
+            # 创建连接, 借助类名，调用 类方法 create_conn
+            my_conn = DBTools.__create_conn()
+            # 创建游标
+            my_cursor = my_conn.cursor()
+            # 执行 sql 语句，做查询
+            my_cursor.execute(sql)
+            # 提取一条记录
+            res = my_cursor.fetchone()
+        except Exception as err:
+            print("执行查询SQL失败：", str(err))
+        finally:
+            # 关闭游标
+            my_cursor.close()
+            # 关闭连接
+            my_conn.close()
+            # 返回查询结果
+            return res
+
+    # 增删改记录
+    @classmethod
+    def db_uid(cls, sql):
+        my_conn = None
+        my_cursor = None
+        try:
+            # 创建连接
+            my_conn = DBTools.__create_conn()
+            # 创建游标
+            my_cursor = my_conn.cursor()
+            # 执行 增删改 语句
+            my_cursor.execute(sql)
+            print("Affected rows:", my_conn.affected_rows())
+            # 提交事务
+            my_conn.commit()
+        except Exception as err:
+            print("执行 增删改 SQL 失败：", str(err))
+            # 回滚事务
+            my_conn.rollback()
+        finally:
+            # 关闭游标
+            my_cursor.close()
+            # 关闭连接
+            my_conn.close()
+
+if __name__ == '__main__':
+    result = DBTools.query_one("select * from t_hero;")
+    print("查询语句的结果：", result)
+
+    DBTools.db_uid("update t_book set `read` = 100 where id = 3;")

案例1.py

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+import pymysql
+db=pymysql.connect (
+    host='localhost',
+    user='root',
+    passwd='114514',
+    database='TESTDB',
+)
+cursor=db.cursor()
+cursor.execute('SELECT VERSION()')
+data = cursor.fetchone()
+print('Database version : %s ' % data)
+cursor.close()
+db.close()

案例2.py

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+import pymysql
+db=pymysql.connect (
+    host='localhost',
+    user='root',
+    passwd='114514',
+    database='TESTDB',
+)
+cursor=db.cursor()
+cursor.execute('DROP TABLE IF EXISTS EMPLOYEE')
+data=cursor.fetchone()
+print(data)
+cursor.close()
+db.close()

案例3.py

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+import pymysql
+db=pymysql.connect (
+    host='localhost',
+    user='root',
+    passwd='114514',
+    database='TESTDB',
+)
+cursor=db.cursor()
+sql="INSERT INTO EMPLOYEE(FIRST_NAME, LAST_NAME, AGE, SEX, INCOME) VALUE ('Mac','Mohan',20,'M',2000)"
+try:
+    cursor.execute(sql)
+    db.commit()
+except:
+    db.rollback()
+db.close()

案例4.py

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+import pymysql
+db=pymysql.connect (
+    host='localhost',
+    user='root',
+    passwd='114514',
+    database='TESTDB',
+)
+cursor=db.cursor()
+sql="SELECT * FROM EMPLOYEE WHERE INCOME > %s" % 1000
+try:
+    cursor.execute(sql)
+    result=cursor.fetchall()
+    for row in result:
+        fname=row[0]
+        lname=row[1]
+        age=row[2]
+        sex=row[3]
+        income=row[4]
+        print(f"fname={fname},lname={lname},age={age},income={income}")
+except:
+    print("Error: unable to fetch data")
+db.close()

案例5.py

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+import pymysql
+db=pymysql.connect (
+    host='localhost',
+    user='root',
+    passwd='114514',
+    database='TESTDB',
+)
+cursor=db.cursor()
+sql="UPDATE EMPLOYEE SET AGE=AGE+1 WHERE SEX = '%c'" % 'M'
+try:
+    cursor.execute(sql)
+    db.commit()
+except:
+    db.rollback()
+db.close()