Question

我有一个表单和存储过程，用于插入表单中的数据。它工作正常，但如果没有填写字段，则不会在SQL中插入NULL，而是插入""。

我尝试过几种不同的方法但似乎没有插入NULL，下面的那些仍会插入""，是否有人能指出我正确的方向？

以下是代码所需的部分，如果您需要更多信息，请告诉我。

Dim rdr As SqlDataReader
            Dim cmdInsert As SqlCommand = New SqlCommand()
            cmdInsert.CommandText = "spPersonalDetailsInsert"
            cmdInsert.CommandType = CommandType.StoredProcedure
            cmdInsert.Connection = connSQL


            Dim firstname, lastname, address, address1, town, county, postcode As SqlParameter
            'convert to null if ""
            Dim frmFirstName As String
            If pd_first_name.Text = "" Then
                frmFirstName = Convert.DBNull
            Else
                frmFirstName = pd_first_name.Text
            End If

            firstname = New SqlParameter()
            firstname.ParameterName = "@firstname"
            firstname.SqlDbType = SqlDbType.NVarChar
            firstname.Size = 50
            firstname.Direction = ParameterDirection.Input
            firstname.Value = frmFirstName

修改

我测试了以下代码：

If pd_first_name.Text = "" Then
            frmFirstName = DBNull.Value
        Else
            frmFirstName = pd_first_name.Text
        End If

但它仍然没有插入NULL所以我测试了这个：

            If pd_first_name.Text = "" Then
                Response.Write("NULL")
                address1.Value = DBNull.Value
            Else
                Response.Write("NOT NULL")
                address1.Value = pd_address1.Text
            End If

因此，如果我在address1字段中不输入任何内容，则应将NULL写入屏幕，但它始终会写入NOT NULL。空表格字段等于什么？在经典ASP中它总是""。

Answer 1

您需要使用DBNull.Value

            If String.IsNullOrEmpty(pd_first_name.Text.ToString().Trim) = true Then
                frmFirstName = DBNull.Value
            Else
                frmFirstName = pd_first_name.Text
            End If

Answer 2

为什么你甚至设置它为null？

        If pd_first_name.Text <> "" Then
          frmFirstName = pd_first_name.Text
          firstname = New SqlParameter()
          firstname.ParameterName = "@firstname"
          firstname.SqlDbType = SqlDbType.NVarChar
          firstname.Size = 50
          firstname.Direction = ParameterDirection.Input
          firstname.Value = frmFirstName
        End If

Answer 3

在我的情况下，使用＆＃39; Nothing＆＃39; 解决了这个问题。像这样使用它

If String.IsNullOrEmpty(pd_first_name.Text) = True Then
   frmFirstName = Nothing
Else
   frmFirstName = pd_first_name.Text
End If

Answer 4

我认为你的问题是frmFirstName是一个字符串而一个字符串不能代表DBNull。

我认为这可以解决您的问题（我刚刚注释掉了您的代码）：

Dim rdr As SqlDataReader
            Dim cmdInsert As SqlCommand = New SqlCommand()
            cmdInsert.CommandText = "spPersonalDetailsInsert"
            cmdInsert.CommandType = CommandType.StoredProcedure
            cmdInsert.Connection = connSQL


            Dim firstname, lastname, address, address1, town, county, postcode As SqlParameter
            'convert to null if ""
            Dim frmFirstName As String
            'If pd_first_name.Text = "" Then
            '    frmFirstName = Convert.DBNull
            'Else
            '    frmFirstName = pd_first_name.Text
            'End If

            firstname = New SqlParameter()
            firstname.ParameterName = "@firstname"
            firstname.SqlDbType = SqlDbType.NVarChar
            firstname.Size = 50
            firstname.Direction = ParameterDirection.Input
            If pd_first_name.Text = "" Then
                  firstname.Value = DBNull.Value
            Else
                  firstname.Value = frmFirstName
            End If

Answer 5

创建存储过程时，将这些列设为null，可以为null。像

CREATE PROCEDURE [dbo].[USP_TDS_SaveRecod]

@ID INT,

@CODE  INT,

@FIRSTNAME VARCHAR(8)=NULL,

@CITY VARCHAR(15)=NULL

AS

BEGIN

    .........................

    .........................

    .........................
END

然后在代码中不添加那些为null的参数。

cmd.Parameters.Add("@ID", SqlDbType.Int).Value = obj.ID;
cmd.Parameters.Add("@CODE", SqlDbType.Int).Value = obj.CODE;
if(pd_first_name.Text != "")
{
    cmd.Parameters.Add("@FIRSTNAME", SqlDbType.VarChar).Value = pd_first_name.Text;
}
if(city.Text != "")
{
    cmd.Parameters.Add("@CITY", SqlDbType.VarChar).Value = pd_first_name.Text;
}

Answer 6

Dim TempStr As String
TempStr= "spPersonalDetailsInsert"
TempStr = TempStr.Replace("''", "null")
cmdInsert.CommandText = TempStr

现在无需使用

If pd_first_name.Text = "" Then
   Response.Write("NULL")
   address1.Value = DBNull.Value
Else
   Response.Write("NOT NULL")
   address1.Value = pd_address1.Text
End If

希望这可能会有所帮助

Answer 7

If RdFree.Checked = True Then
    Dim nu As String = "NULL"
    UpdPolicys.Append(", AccIDFree = " & nu & " , AccTypeIDFree = " & nu & " ")
End If

如果表单字段为空，如何将NULL插入数据库

7 个答案: