Question

我有桌子“学生”

   P_ID   LastName  FirstName  Address  City

   1        Hansen    Ola                
   2        Svendson   Tove
   3        Petterson   Kari
   4        Nilsen       Johan
...and so on

如何更改C＃中的编辑代码

 string firstName = "Ola";
 string  lastName ="Hansen";
 string  address = "ABC";
 string city = "Salzburg";

 string connectionString = System.Configuration.ConfigurationManager
                          .ConnectionStrings["LocalDB"].ConnectionString;

 using (SqlConnection connection = new SqlConnection(connectionString))
     using (SqlCommand command = connection.CreateCommand())
 { 
   command.CommandText = "INSERT INTO Student (LastName, FirstName, Address, City) 
                          VALUES (@ln, @fn, @add, @cit)";

   command.Parameters.AddWithValue("@ln", lastName);
   command.Parameters.AddWithValue("@fn", firstName);
   command.Parameters.AddWithValue("@add", address);
   command.Parameters.AddWithValue("@cit", city);

   connection.Open();

   command.ExecuteNonQuery();

   connection.Close();
 }

编辑条目，其中姓氏字段具有姓氏值， FirstName 字段具有名字值。

我不想像这样使用

 UPDATE Persons  SET Address='Nissestien 67', City='Sandnes' 
 WHERE LastName='Tjessem'     AND FirstName='Jakob'

我将我的原始陈述编辑为

 command.CommandText = "UPDATE Student(LastName, FirstName, Address, City) 
   VALUES (@ln, @fn, @add, @cit) WHERE LastName='" + lastName + 
                           "' AND FirstName='" +  firstName+"'";

但声明没有被执行，为什么它会抛出SQL异常？有没有解决方案呢？

Answer 1

这不是更新SQL中记录的正确方法：

command.CommandText = "UPDATE Student(LastName, FirstName, Address, City) VALUES (@ln, @fn, @add, @cit) WHERE LastName='" + lastName + "' AND FirstName='" + firstName+"'";

你应该这样写：

command.CommandText = "UPDATE Student 
SET Address = @add, City = @cit Where FirstName = @fn and LastName = @add";

然后添加与为插入操作添加的参数相同的参数。

Answer 2

我不想像这样使用

这是SQL中Update语句的语法，您必须使用该语法，否则您将获得异常。

command.Text = "UPDATE Student SET Address = @add, City = @cit Where FirstName = @fn AND LastName = @ln";

然后相应地添加您的参数。

command.Parameters.AddWithValue("@ln", lastName);
command.Parameters.AddWithValue("@fn", firstName);
command.Parameters.AddWithValue("@add", address);
command.Parameters.AddWithValue("@cit", city);

Answer 3

每种语言都有适当的语法。类似地，SQL（结构化查询语言）也具有更新查询的特定语法，如果我们想要使用更新查询，我们必须遵循这些语法。否则它不会给出预期的结果。

Answer 4

string constr = @"Data Source=(LocalDB)\v11.0;Initial Catalog=Bank;Integrated Security=True;Pooling=False";
SqlConnection con = new SqlConnection(constr);
DataSet ds = new DataSet();
con.Open();
SqlCommand cmd = new SqlCommand(" UPDATE Account  SET name = Aleesha, CID = 24 Where name =Areeba and CID =11 )";
cmd.ExecuteNonQuery();

Answer 5

请永远不要使用这个连续表格：

String st = "UPDATE supplier SET supplier_id = " + textBox1.Text + ", supplier_name = " + textBox2.Text
        + "WHERE supplier_id = " + textBox1.Text;

使用：

command.Parameters.AddWithValue("@attribute", value);

始终以工作为导向

编辑：这是因为当您参数化更新时，它有助于防止SQL注入。

Answer 6

如果您不想使用SQL语法（您不得不使用），那么请切换到Entity Framework或Linq-to-SQL之类的框架，您不需要自己编写SQL语句。

Answer 7

command.Text = "UPDATE Student 
  SET Address = @add, City = @cit
  Where FirstName = @fn and LastName = @add";

Answer 8

private void button4_Click(object sender, EventArgs e)
    {
        String st = "DELETE FROM supplier WHERE supplier_id =" + textBox1.Text;

        SqlCommand sqlcom = new SqlCommand(st, myConnection);
        try
        {
            sqlcom.ExecuteNonQuery();
            MessageBox.Show("刪除成功");
        }
        catch (SqlException ex)
        {
            MessageBox.Show(ex.Message);
        }
    }



    private void button6_Click(object sender, EventArgs e)
    {
        String st = "SELECT * FROM suppliers";

        SqlCommand sqlcom = new SqlCommand(st, myConnection);
        try
        {
            sqlcom.ExecuteNonQuery();
            SqlDataReader reader = sqlcom.ExecuteReader();
            DataTable datatable = new DataTable();
            datatable.Load(reader);
            dataGridView1.DataSource = datatable;
            //MessageBox.Show("LEFT OUTER成功");
        }
        catch (SqlException ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

Answer 9

SELECT Price FROM Pricing WHERE start_date >= '2015-05-30' AND end_date <= '2015-06-02'

C＃中的SQL更新语句

9 个答案: