VB 2010 OleDbCommand具有我为空的参数 [英] VB 2010 OleDbCommand with parameter that me be null

问题描述

你好.

我有以下代码:

Hello.

I have this code:

Dim conz As New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Bdados\CV_PARTS.accdb;Persist Security Info=False")
Dim cmd As New OleDbCommand("SELECT * FROM PECAS_IN WHERE Fornecedor = ?)", conz)

之后，我创建一个参数并将其分配给组合框的文本.假设我想通过将组合框保留为空来检索所有数据，我应该使用什么代码?我试过了:

After this I create a parameter and assign it to the text of a combobox. Supposing I want to retrieve all data by leaving the combobox empty what code should I use? I tried:

Dim cmd As New OleDbCommand("SELECT * FROM PECAS_IN WHERE (Fornecedor = ? OR Fornecedor Like "*")

但这是行不通的.正确的语法是什么?

谢谢.
Octavio

But it does not work. What is the correct syntax?

Thank you.
Octavio

推荐答案

首先，您不能在VB中使用像这样的双引号.

试试

First of all, you can''t use double quote like this in VB.

Try

Dim cmd As New OleDbCommand("SELECT * FROM PECAS_IN WHERE (Fornecedor = ? OR Fornecedor Like ""*""")

您好.

我尝试了您的解决方案，但仍然无法正常工作...

Octavio

Hello.

I tried your solution but it still does not work...

Octavio

嗨.

我发现了！

Hi.

I found out!

Dim cmd As New OleDbCommand("SELECT * FROM PECAS_IN WHERE Fornecedor LIKE ''%'' + ? + ''%''"

有点奇怪，但确实有效.就像在Oracle上使用SQL一样.

It''s a bit weird but it does work. Nothing like using SQL on Oracle, which is what i''m used to.

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