检测“空”。数据库字段 [英] Detecting "Null" database fields

问题描述

我正在使用SQL Server 2000并且在我的页面上，我只是创建一个

SQLDataReader并用检索到的（单个）记录填充标签。

但是，当字段为空时，如何防止出错？

我尝试过这样的事情（试验IsDBNull）：

=== =============================================== === ====

如果dtrData.IsDBNull（" Address2"）= True则

lblAddress2.Text =""

Else

lblAddress2.Text = dtrData（" Address2"）

结束如果


这个......


如果IsNothing（dtrDatal（" Address2"））= True则

lblAddress2.Text =""

Else

lblAddress2.Text = dtrData（" Address2"）

结束如果

=============== =================================== ======

。 ..似乎都不起作用。有什么建议？谢谢！

I''m using SQL Server 2000 and on my page, I''m simply creating a
SQLDataReader and filling in Labels with the retrieved (single) record.
However, how can I prevent from getting errors when a field is null?
I''ve tried something like this (experimenting with IsDBNull):
================================================== =======
If dtrData.IsDBNull("Address2") = True Then
lblAddress2.Text = ""
Else
lblAddress2.Text = dtrData("Address2")
End If

And this....

If IsNothing(dtrDatal("Address2")) = True Then
lblAddress2.Text = ""
Else
lblAddress2.Text = dtrData("Address2")
End If
================================================== ======
...and neither seem to work. Any suggestions? Thanks!

推荐答案

你可以使用


选择ISNULL（地址2） ，''''）你的SELECT语句中的地址2 FROM MyTable


或者只是在读取数据时使用它：


lblAddress2.Text ="" + dtrData（Addres2）


Dale


" D. Shane Fowlkes < SH ********** @ h-o-t-m-a-i-l.com>在消息中写道

新闻：％2 **************** @ TK2MSFTNGP09.phx.gbl ...

You can use

Select ISNULL(Address2, '''') AS Address2 FROM MyTable

in your SELECT statement or just use this when reading the data:

lblAddress2.Text = "" + dtrData("Addres2")

Dale

"D. Shane Fowlkes" <sh**********@h-o-t-m-a-i-l.com> wrote in message
news:%2****************@TK2MSFTNGP09.phx.gbl...

我'我正在使用SQL Server 2000并在我的页面上，我只是创建一个
SQLDataReader并使用检索到的（单个）记录填充标签。
但是，如何防止错误field是null？

我尝试过类似的东西（试验IsDBNull）：
==================== ============================== =======
如果dtrData.IsDBNull（" Address2" ）= True然后
lblAddress2.Text =""
Else
lblAddress2.Text = dtrData（" Address2"）
结束如果

而这......

如果IsNothing（dtrDatal（" Address2"））= True那么
lblAddress2.Text =""
其他
lblAddress2 .Text = dtrData（" Address2"）
结束如果
============================== ==================== ======

..似乎都不起作用。有什么建议？谢谢！

I''m using SQL Server 2000 and on my page, I''m simply creating a
SQLDataReader and filling in Labels with the retrieved (single) record.
However, how can I prevent from getting errors when a field is null?
I''ve tried something like this (experimenting with IsDBNull):
================================================== =======
If dtrData.IsDBNull("Address2") = True Then
lblAddress2.Text = ""
Else
lblAddress2.Text = dtrData("Address2")
End If

And this....

If IsNothing(dtrDatal("Address2")) = True Then
lblAddress2.Text = ""
Else
lblAddress2.Text = dtrData("Address2")
End If
================================================== ======
..and neither seem to work. Any suggestions? Thanks!

我的代码通常更像是（C＃）


if（dr [" field"] == DBNull.Value）

声明;

else

声明;


等于（VB.NET）


If（dr（" field"）== DBNull.Value）然后

Else

结束如果


根据建议，如果你想用字符串填充

，你也可以在SQL语句中执行此操作你正在做。


-

Gregory A. Beamer

MVP; MCP：+ I，SE，SD，DBA


**************************** ********************** ********************

在盒子外面思考！

************************************* ************* ********************

D。 Shane Fowlkes < SH ********** @ h-o-t-m-a-i-l.com>在消息中写道

新闻：％2 **************** @ TK2MSFTNGP09.phx.gbl ...

My code is normally more like so (C#)

if(dr["field"] == DBNull.Value)
statement;
else
statement;

Which equates to (VB.NET)

If (dr("field") == DBNull.Value) Then
Else
End If

As suggested, you can also do this in the SQL statement if you want to fill
with a string, as you are doing.

--
Gregory A. Beamer
MVP; MCP: +I, SE, SD, DBA

************************************************** ********************
Think Outside the Box!
************************************************** ********************
"D. Shane Fowlkes" <sh**********@h-o-t-m-a-i-l.com> wrote in message
news:%2****************@TK2MSFTNGP09.phx.gbl...

我'我正在使用SQL Server 2000并在我的页面上，我只是创建一个
SQLDataReader并使用检索到的（单个）记录填充标签。
但是，如何防止错误field是null？

我尝试过类似的东西（试验IsDBNull）：
==================== ============================== =======
如果dtrData.IsDBNull（" Address2" ）= True然后
lblAddress2.Text =""
Else
lblAddress2.Text = dtrData（" Address2"）
结束如果

而这......

如果IsNothing（dtrDatal（" Address2"））= True那么
lblAddress2.Text =""
其他
lblAddress2 .Text = dtrData（" Address2"）
结束如果
============================== ==================== ======

..似乎都不起作用。有什么建议？谢谢！

I''m using SQL Server 2000 and on my page, I''m simply creating a
SQLDataReader and filling in Labels with the retrieved (single) record.
However, how can I prevent from getting errors when a field is null?
I''ve tried something like this (experimenting with IsDBNull):
================================================== =======
If dtrData.IsDBNull("Address2") = True Then
lblAddress2.Text = ""
Else
lblAddress2.Text = dtrData("Address2")
End If

And this....

If IsNothing(dtrDatal("Address2")) = True Then
lblAddress2.Text = ""
Else
lblAddress2.Text = dtrData("Address2")
End If
================================================== ======
..and neither seem to work. Any suggestions? Thanks!

尝试：


如果（您的参数名称）是System.DBNull。然后价值

lblAddress2.text =""

else

lblAddress2.text =（您的参数名称）

结束如果

D。 Shane Fowlkes < SH ********** @ h-o-t-m-a-i-l.com>在消息中写道

新闻：％2 **************** @ TK2MSFTNGP09.phx.gbl ...

Try:

if (your parameter name) is System.DBNull.Value then
lblAddress2.text = ""
else
lblAddress2.text = (your parameter name)
end if
"D. Shane Fowlkes" <sh**********@h-o-t-m-a-i-l.com> wrote in message
news:%2****************@TK2MSFTNGP09.phx.gbl...

我'我正在使用SQL Server 2000并在我的页面上，我只是创建一个
SQLDataReader并使用检索到的（单个）记录填充标签。
但是，如何防止错误field是null？

我尝试过类似的东西（试验IsDBNull）：
==================== ============================== =======
如果dtrData.IsDBNull（" Address2" ）= True然后
lblAddress2.Text =""
Else
lblAddress2.Text = dtrData（" Address2"）
结束如果

而这......

如果IsNothing（dtrDatal（" Address2"））= True那么
lblAddress2.Text =""
其他
lblAddress2 .Text = dtrData（" Address2"）
结束如果
============================== ==================== ======

..似乎都不起作用。有什么建议？谢谢！

I''m using SQL Server 2000 and on my page, I''m simply creating a
SQLDataReader and filling in Labels with the retrieved (single) record.
However, how can I prevent from getting errors when a field is null?
I''ve tried something like this (experimenting with IsDBNull):
================================================== =======
If dtrData.IsDBNull("Address2") = True Then
lblAddress2.Text = ""
Else
lblAddress2.Text = dtrData("Address2")
End If

And this....

If IsNothing(dtrDatal("Address2")) = True Then
lblAddress2.Text = ""
Else
lblAddress2.Text = dtrData("Address2")
End If
================================================== ======
..and neither seem to work. Any suggestions? Thanks!

这篇关于检测“空”。数据库字段的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！