ADO.net学习基础 增删改

 string connString1 = "Data Source =.\\SQLEXPRESS2014;Initial Catalog = StudentManageDB;Integrated Security = True";//windows身份登陆，只限于本机
            string connString = "Server = .\\SQLEXPRESS2014;DataBase = StudentManageDB;Uid = sa;Pwd = sa";//SQLServer身份登陆
            //本机：如果是默认数据库实例，则可以省略实例名,写成 “.”或者“localhost”；非默认的话，写上实例名，一般是计算机名（可以用“.”/"localhost"代替）+ 实例名
            //远程的话：先写远程连接的ip地址，然后加数据库实例名（如果是默认数据库实例，则可以省略实例名）

        //如果有端口号，则ip地址加逗号加端口号；默认1433
            //C#不识别单个"\"，所以使用“\\”，或者在字符串前面添加“@”；
            SqlConnection conn = new SqlConnection(connString);
            conn.Open();//打开连接
            //使用Command对象，增删改查的操作。Command的两个属性，Connection(连接对象),CommandText(sql语句，或者存储过程名称)
            //方法：ExecuteNonQuery();执行增删改操作；ExecuteScalar();返回单一结果的查询；ExecuteReader();返回只读数据列表的查询
            //ExecuteNonQuery();执行后返回受影响的行数，一般是大于0的整数，等于0说明没有影响，-1表示执行出错
            string sql1 = "insert into students(StudentName, Gender, Birthday, StudentIdNo, Age, PhoneNumber, StudentAddress, ClassId)" +
                    " values('Jerry', 'm', '1991-02-11', 123456789, 28, 1777777777, 'Beijing', 4545)";
            string sql2 = "delete from students where StudentName = 'Jerry'";
            
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = conn;
            cmd.CommandText = sql1 + ";" + sql2;//如果要执行多条sql语句，只需要用“;”连接起来即可
            int num = cmd.ExecuteNonQuery();
            Console.WriteLine(num);//结果是2
            //ExecuteScalar():同时执行insert和select
            string sql3 = "insert into students(StudentName, Gender, Birthday, StudentIdNo, Age, PhoneNumber, StudentAddress, ClassId)" +
                   " values('Jim', 'm', '1980-02-11', 56789123, 40, 1777777777, 'Beijing', 4545); select @@identity";
            //@@identity是数据库中的一个全局变量，里面保存着最近一次生成的标识列的值
            cmd.CommandText = sql3;
            int identity = Convert.ToInt32(cmd.ExecuteScalar());
            Console.WriteLine(identity);
            conn.Close();//关闭连接