C#中的SqlCommd的用法

SqlCommand这个对象可以让我们在对数据库的表进行增删改查操作。

声明SqlCommond对象

SqlCommand command = new SqlCommand(sql, conn);

sql操作数据库返回一条语句的代码为

            SqlConnection conn = new SqlConnection("server=PC201908182326;database=NorthWind;uid=sa;pwd=123456");
            DataContext context = new DataContext(conn);
            string sql = @"insert into Customers(ContactName,City) values('a','b')";
            SqlCommand command = new SqlCommand(sql, conn);
            conn.Open();
            int i = command.ExecuteNonQuery();
            conn.Close();
            Console.WriteLine($"插入{i}行");

sql操作数据库返回一张表的代码为

            SqlConnection conn = new SqlConnection("server=PC201908182326;database=NorthWind;uid=sa;pwd=123456");
            DataContext context = new DataContext(conn);
            string sql = @"select * from Customers";
            SqlCommand command = new SqlCommand(sql, conn);
            conn.Open();
            SqlDataReader reader = command.ExecuteReader();
            while (reader.Read())
            {
                Console.WriteLine($"顾客ID：{reader[0]},顾客名：{reader[1]},城市：{reader[2]}");
            }
            conn.Close();

sql操作数据库返回一条数据的代码为

            SqlConnection conn = new SqlConnection("server=PC201908182326;database=NorthWind;uid=sa;pwd=123456");
            DataContext context = new DataContext(conn);
            string sql = @"select City from Customers where CustomerID =1";
            SqlCommand command = new SqlCommand(sql, conn);
            conn.Open();
            string str = command.ExecuteScalar().ToString();
            conn.Close();
            Console.WriteLine($"城市名为：{str}");

连接池关闭开启

            conn.Open();
            conn.Close();