Question

我有存储过程允许空参数，并在SSMS中正常工作。。这是SP

ALTER PROCEDURE [dbo].[sp_RepInventorySales]
@SalesOrderNo varchar(9) = null
AS
BEGIN
SELECT SalesOrderNo, ItemCode, ContainerNo, SealNo, ContainerType, OrderQty
FROM  SalesOrderDetail 
where SalesOrderNo = isnull(@SalesOrderNo, SalesOrderNo )

实际上SP是我的水晶报告的来源。当Me.txtSalesOrderNo.Text非空时，我得到正确的输出。但是，如果textbox为空，则存储过程将参数视为空字符串''。如何将空字符串替换为NULL？。这是代码VB代码

Private Dset As DataSet 
Private Da As SqlDataAdapter 

  Dim objRpt As New RepInventorySales /*used for crystal report*/
    Dset = New DataSet

Da = New SqlDataAdapter("sp_RepInventorySales '" & trim(Me.txtSalesOrderNo.Text) & "' ", Conn_DB)
 Da.Fill(Dset)
        If Dset.Tables(0).Rows.Count <> 0 Then
            objRpt.SetDataSource(Dset.Tables(0))

我尝试在SqlDataAdapter中的查询字符串中使用IIF将空字符串替换为null但是给了我错误

            Da = New SqlDataAdapter("sp_RepInventorySales '" & Trim(Me.IIf(txtTextBox.Text Is Nothing, Null, txtTextBox.Text).Text) & "' ", Conn_DB)

这是最终的解决方案。谢谢你的帮助！

IF @SalesOrderNo = ''
    SET @SalesOrderNo = NULL
IF @ContainerType = ''
    SET @ContainerType = NULL

SELECT SalesOrderNo, ItemCode, ContainerNo, SealNo, ContainerType, OrderQty
FROM SalesOrderDetail
WHERE ( SalesOrderNo = @SalesOrderNo OR @SalesOrderNo IS NULL )
      AND
      ( ContainerType = @ContainerType OR @ContainerType IS NULL )

Answer 1

改为使用DBNull.Value。

IF ELSE方法：（在调用 New SqlDataAdapter之前验证并分配，因此在sql适配器中不需要IIF，只需分配价值textbox）

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

How to insert NULL into database if form field is empty

DBNull.Value

Answer 2

您将始终获得空字符串，因为您将参数作为硬编码字符串传递到单引号..."sp_RepInventorySales '" & trim(Me.txtSalesOrderNo.Text) & "'...

中

正确地将参数添加到SqlDataAdapter.SelectCommand.Parameters集合，然后您可以使用DBNull.Value

Da = New SqlDataAdapter("sp_RepInventorySales", Conn_DB)
DA.SelectCommand.CommandType = CommandType.StoredProcedure
'Parameter's type need to be Object because DBNull.Value cannot be converted to string
Dim paramValue as Object = DirectCast(DBNull.value, Object)
If String.IsNullOrEmpty(Me.txtSalesOrderNo.Text) = false Then
    paramValue = Me.txtSalesOrderNo.Text.Trim()
End If
Dim param As New SqlParameter With {.ParameterName = "@SalesOrderNo",
                                    .SqlDbType = SqlDbType.VarChar,
                                    .Value = paramValue}
DA.SelectCommand.Parameters.Add(param)
Da.Fill(Dset)

Answer 3

我用解决方案改进了你的方法，你可以试试这个

  Sub fun()
        Dim Dset As DataSet
        Dim Da As PgSqlDataAdapter
        Dim strParam As Object
        Dim objRpt As New crptAccountlist
        Dset = New DataSet
        If Trim(txtSalesOrderNo.Text) <> vbNullString Then
            strParam = Trim(txtSalesOrderNo.Text)
        Else
            strParam = DBNull.Value
        End If
        Da = New PgSqlDataAdapter("", Conn_DB)
        With Da
            .SelectCommand.CommandType = CommandType.StoredProcedure
            .SelectCommand.CommandText = "sp_RepInventorySales"
            .SelectCommand.Parameters.AddWithValue("@SalesOrderNo", strParam)
        End With
        Da.Fill(Dset)
    End Sub

请参阅此Demo

Answer 4

只是将条件放在你的SP上

   IF @SalesOrderNo = '' SET @SalesOrderNo = null 
   IF @ContainerType= '' SET @ContainerType= null 
   SELECT SalesOrderNo, ItemCode, ContainerNo, SealNo, ContainerType, OrderQty
   FROM  SalesOrderDetail 
   where SalesOrderNo = @SalesOrderNo AND ContainerType = @ContainerType

如何在存储过程和VB.net中将空字符串参数替换为Null

4 个答案: