MySql DB更新问题 | DB更新问题

本文介绍了MySql DB更新问题的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

您好。我有一点问题。

当我尝试将数据输入表格时，我在mysql数据库中编写程序，我收到此警告。当数据库数据部分为NULL时，我收到此错误。问题不会返回空。

Hi. I have a little problem.

I wrote programs in mysql database when I try to enter data into a table, I get this warning. I get this error when the database data section is NULL. The problem does not return empty.

Quote：

错误：DBNull类型和对于字符串'='运算符未定义

Error: DBNull type and for the string '=' operator is not defined

我的更新代码：

my update code:

Dim Table As String = ini.ReadValue("COMM", "DBTable")
Dim Data As String = "CODE_NO='" + DataGridView1.Item(0, i).Value.ToString
Dim con As New MySqlConnection
Dim Comm As New MySqlCommand

Comm = New MySqlCommand("UPDATE " + Table + " SETKAY='" + Label4.Text + "'" + ", STATUS='Waiting', DATE='" + DateTime.Now.ToString + "'" + " WHERE " + Data + "'", con)

数据库表格单元状态=（NULL）（不工作）

Database Table cell status= (NULL) ( not working )

<br />
Database Table cell status= " "

（工作）

谢谢大家。但不明白每个解决方案。我想告诉你的照片。

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( Working )

Thanks everyone. But dont understand every solution. I want to tell with your pictures.
http://tinypic.com/view.php?pic=2ljhqwk&s=8#.VFaaw01yZ9A[^]
http://tinypic.com/view.php?pic=wircd5&s=8#.VFaa3U1yZ9A[^]

推荐答案

Dim Data As String = "IFNULL(CODE_NO,'')=@Item"

另请参考]

Dim Query As String = "Update YourDB.my_table_name SET Value1=@V1, Value2=@V2 Where Value3=@Condition;"
Parameters.AddWithValue("@V1", "Value Of 1")
Parameters.AddWithValue("@V2", "Value Of 2")
Parameters.AddWithValue("@Condition", 0)

然后Executenonquery（）启动你的命令行动。

你可以看到关于MySQL的进一步解释，我也回答了。我希望它能帮助你开始朝着正确的方向前进。但在进一步研究之前，你将不得不做一些研究和研究基础知识。

Then Executenonquery() to initiate your action on your command.

You can see further explanation on MySQL covered in this Answer, also answered by me. I hope it helps get you started in the right direction. But you are going to have to do some research and study the basics before going further with this.

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