Question

这是我的代码。我试图获得存储在query1变量中的SQL查询的结果，并希望将该结果用于存储在query变量中的SQL查询中。 Messagebox是无关紧要的，我只是编写它以查看我是否从listbox1获得了正确的结果。如果我将query1的结果硬编码为命令参数，它可以很好地工作。

private void btnAddCoarse_click(object sender, EventArgs e)
{
    MessageBox.Show(listBox1.SelectedItem.ToString());


    string query1 ="SELECT ogrenciNo FROM ders,ogrenci,Enrollment WHERE ogrenciId=ogrenciNo AND dersId=dersKodu AND ogrenci.email='" + mainform.Username + "' AND Enrollment.dersId='"+listBox1.SelectedValue+"'";
    string query = "INSERT INTO Enrollment(dersId,ogrenciId) VALUES (@dersId, @ogrenciId)";

    using (connection = new SqlConnection(connectionString))
    using (SqlCommand command = new SqlCommand(query, connection))
    {
        connection.Open();

        command.Parameters.AddWithValue("@dersId", listBox1.SelectedValue);
        command.Parameters.AddWithValue("@ogrenciId",//this is where i need the query1//);
        command.ExecuteNonQuery();
        PopulateList2();
    }
}

Answer 1

您只需要一个sql命令。结构将是这样的：

insert into table2
(field1, field2)
select value1, value2
etc

Answer 2

 int id;   
 using (connection = new SqlConnection(connectionString))
           using (SqlCommand command = new SqlCommand(query1, connection))
           {
             connection.Open();
             id = Convert.ToInt32(command.ExecuteScalar()); //I guess it returns only 1 id?..  
           }

Answer 3

尝试这样做

private void btnAddCoarse_click(object sender, EventArgs e)
{
       //MessageBox.Show(listBox1.SelectedItem.ToString());


       string query1 ="SELECT ogrenciNo FROM ders,ogrenci,Enrollment WHERE ogrenciId=ogrenciNo AND dersId=dersKodu AND ogrenci.email='" + mainform.Username + "' AND Enrollment.dersId='"+listBox1.SelectedValue+"'";
       string query = "INSERT INTO Enrollment(dersId,ogrenciId) VALUES (@dersId, @ogrenciId)";



       using (connection = new SqlConnection(connectionString))
       {
            int result=0;
            using (SqlCommand command = new SqlCommand(query1, connection))
            {
                connection.Open();

                result=Convert.ToInt32(command.ExecuteScalar());
                connection.Close();
            }
            using (SqlCommand command = new SqlCommand(query, connection))
            {
                connection.Open();

                command.Parameters.AddWithValue("@dersId", listBox1.SelectedValue);
                command.Parameters.AddWithValue("@ogrenciId",result);
                command.ExecuteNonQuery();
                PopulateList2();
            }
        }

}

将查询结果导入变量，然后将其传递给命令

3 个答案: