获取错误执行查询 [英] Getting error executenonquery

问题描述

它应该减去BagQty的数量，但是我得到了这个ExecuteNonQuery错误



我试过的：



名称空间BagQtyPractice

{

公共部分类Form1：表格

{

SqlConnection con = new SqlConnection（Server = DESKTOP-1281SGB; Database = Practice; User Id = KicuCrafts; Password = admin;）;

SqlDataAdapter sda;

SqlCommandBuilder scb;

DataTable dt;

public Form1（）

{



InitializeComponent（）;

}



private void btnAddtoCart_Click（object sender，EventArgs e ）

{

SqlCommand cmd = con.CreateCommand（）;

cmd.CommandType = CommandType.Text;

cmd.CommandText =更新BagPracticeQty设置BagQty = BagQty- + txtQTY.Text;

cmd.ExecuteNonQuery（）;

}

It is supposed to subtract the Quantity of BagQty but I'm getting this ExecuteNonQuery error

What I have tried:

namespace BagQtyPractice
{
public partial class Form1 : Form
{
SqlConnection con = new SqlConnection("Server=DESKTOP- 1281SGB;Database=Practice;User Id=KicuCrafts; Password = admin; ");
SqlDataAdapter sda;
SqlCommandBuilder scb;
DataTable dt;
public Form1()
{

InitializeComponent();
}

private void btnAddtoCart_Click(object sender, EventArgs e)
{
SqlCommand cmd = con.CreateCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = "update BagPracticeQty set BagQty=BagQty-" + txtQTY.Text;
cmd.ExecuteNonQuery();
}

推荐答案

不要这样做像那样！永远不要连接字符串来构建SQL命令。它让您对意外或故意的SQL注入攻击持开放态度，这可能会破坏您的整个数据库。总是使用参数化查询。



连接字符串时会导致问题，因为SQL会收到如下命令：

Don't do it like that! Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

就SQL而言，用户添加的引号会终止字符串，并且您会遇到问题。但情况可能更糟。如果我来并改为输入：x'; DROP TABLE MyTable; - 然后SQL收到一个非常不同的命令：

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

哪个SQL看作三个单独的命令：

Which SQL sees as three separate commands:

SELECT * FROM MyTable WHERE StreetAddress = 'x';

完全有效的SELECT

A perfectly valid SELECT

DROP TABLE MyTable;

完全有效的删除表格通讯和

A perfectly valid "delete the table" command

--'

其他一切都是评论。

所以它确实：选择任何匹配的行，从数据库中删除表，并忽略其他任何内容。



所以总是使用参数化查询！或者准备好经常从备份中恢复数据库。你经常定期备份，不是吗？



一旦你修复了整个应用程序 - 并且错过了一个实例并且你有风险 - 你可能会发现你的问题已经消失了。

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

Once you have fixed that throughout you app - and miss one instance and you are at risk - you will probably find that your problem has disappeared.

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