带有条件的SUM SQL列 [英] SUM SQL column with conditions

问题描述

您好，能帮我查询一下sql吗？我尝试将列Cas与2个条件相加。 sql中的记录存在但没有找到。



谢谢



我尝试过：

Hello, can you help me with sql query. I try to sum column "Cas" with 2 conditions. Records in sql exist but nothing found.

thank you

What I have tried:

Dim conn As New SqlConnection(connstring)
        Dim cnn As New ADODB.Connection
        Dim rs As New ADODB.Recordset
        Dim time As DateTime = DateTime.Now
        Dim dates As String = "yyyy-MM-dd"

        Try
            conn.Open()
        Catch
            MsgBox("Připojení k databázi se nezdařilo.", , "Chyba")
        End Try

        Dim COMMAND2 As String = (("SELECT case SUM(Cas) FROM nvsp_bar_automaticky_tisk_zamestnanci WHERE CisloZam = '" & TextBox1.Text & "'  AND (CONVERT(DATETIME,CONVERT(INT,Datum))) = '" & time.ToString(dates) & "'"))
        
        Dim DA2 As New SqlDataAdapter(CMD2)
        Dim TABLE2 As New DataTable
        If TABLE2.Rows.Count > 0 Then
            'SLOUPEC Z TABULKY 3
            Refresh()
            DA2.Fill(TABLE2)
            Label2.Text = TABLE2.Rows(0)(0).ToString()
        Else
            MsgBox("Číslo karty nenalezeno",, "Chyba")
        End If
        conn.Close()

    End Sub

推荐答案

对于初学者，不要这样做！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。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：

For starters, 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？



当你通过整个应用程序修复它时，你可以开始解决你的问题 - 这就是你除非您尝试使用实际的CASE WHEN语句，否则不要在其中使用CASE一词。 SQL CASE声明 [ ^ ]

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?

When you've fixed that through your whole app, you can start to fix your problem - which is that you don't need the word "CASE" in there, unless you are trying to use an actual CASE WHEN statement. SQL CASE Statement[^]

建议：打印生成的SQL查询字符串以检查它是否符合您的预期，或使用调试器。

Advice: print the resulting SQL query string to check that it is what you expect, or use the debugger.

COMMAND2 = (("SELECT case SUM(Cas) FROM nvsp_bar_automaticky_tisk_zamestnanci WHERE CisloZam = '" & TextBox1.Text & "'  AND (CONVERT(DATETIME,CONVERT(INT,Datum))) = '" & time.ToString(dates) & "'"))

不是你问题的解决方案，而是你遇到的另一个问题。

永远不要建立一个通过连接字符串进行SQL查询。迟早，您将使用用户输入来执行此操作，这会打开一个名为SQL注入的漏洞，这对您的数据库很容易并且容易出错。

名称中的单引号你的程序崩溃。如果用户输入像Brian O'Conner这样的名称可能会使您的应用程序崩溃，那么这是一个SQL注入漏洞，崩溃是最少的问题，恶意用户输入，并且它被提升为具有所有凭据的SQL命令。

SQL注入 - 维基百科 [ ^ ]

SQL注入 [ ^ ]

按示例进行SQL注入攻击 [ ^ ]

PHP：SQL注入 - 手册 [ ^ ]

SQL注入预防备忘单 - OWASP [ ^ ]

我该怎么办？解释没有技术术语的SQL注入？ - 信息安全堆栈交换 [ ^ ]

Not a solution to your question, but another problem you have.
Never build an SQL query by concatenating strings. Sooner or later, you will do it with user inputs, and this opens door to a vulnerability named "SQL injection", it is dangerous for your database and error prone.
A single quote in a name and your program crash. If a user input a name like "Brian O'Conner" can crash your app, it is an SQL injection vulnerability, and the crash is the least of the problems, a malicious user input and it is promoted to SQL commands with all credentials.
SQL injection - Wikipedia[^]
SQL Injection[^]
SQL Injection Attacks by Example[^]
PHP: SQL Injection - Manual[^]
SQL Injection Prevention Cheat Sheet - OWASP[^]
How can I explain SQL injection without technical jargon? - Information Security Stack Exchange[^]

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