修改忽略.idea

example/pymysql_CRDU_student.py

@@ -9,37 +9,60 @@
 '''
 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
-    :param db: 数据库链接对象
-    :return:
-    """
-    cursor = db.cursor()
-    cursor.execute("DROP TABLE IF EXISTS student;")
+    """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 
-                                );"""
-    cursor.execute(sql)
-    cursor.close()
+                                );"""       # 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()
+        db.commit()     # 插入操作必须提交事务才能成功
         cursor.close()
     except:
-        db.rollback()
+        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)
@@ -54,6 +77,7 @@ def delete_db(db:pymysql.connect):
 
 
 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)
@@ -69,27 +93,31 @@ def update_db(db:pymysql.connect):
 
 
 if __name__ == '__main__':
-    db = pymysql.connect(host="127.0.0.1", port=3306, user='root', password="123123", charset="utf8",
-                         database="student")  # 链接数据库
-
-    create_table(db)
-
-    insert_table(db)
-
-    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
+    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