带有变量的sql命令where case [英] Sql command with with variable where case

问题描述

欢迎，

我正在开发一个项目，根据几个条件选择过滤



如从db中选择.......和......和.....



我已计算出条件是否超过200条件



我正在考虑这个SQL语句

 Dim cmd As New SqlCommand（ select * from T_Data where& TextBox5.Text&order by TtitleInt，TNatInt，TName，mysqlconnection）

< b>我尝试了什么：



它仅适用于整数

解决方案

从不去做！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。改为使用参数化查询。



连接字符串时会导致问题，因为SQL会收到如下命令：

  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：

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

哪个SQL看作三个单独的命令：

  SELECT  *  FROM  MyTable  WHERE  StreetAddress = '  x'; 

完全有效的SELECT

  DROP   TABLE  MyTable; 

完全有效的删除表格通讯和

   -   ' 

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。你定期做备份，不是吗？



相信我，正确地完成这项工作要比尝试解决它的混乱要少得多。发生！

Welcome ,
I'm working on a project with option of filtering depending on few conditions

such as select from db where ....... and ...... and .....

I have calculated if conditions and they will be over 200 conditions

I'm thinking of this SQL statement

Dim cmd As New SqlCommand("select * from T_Data where " & TextBox5.Text & " order by TtitleInt , TNatInt , TName ", mysqlconnection)

What I have tried:

it's working only for integers

解决方案

Never do 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. Use Parametrized queries instead.

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

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

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;--'

Which SQL sees as three separate commands:

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

DROP TABLE MyTable;

A perfectly valid "delete the table" command

--'

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?

Trust me, it's a lot less work to do the job properly than to try and sort out the mess when it occurs!

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