如何创建参数化 SQL 查询？我为什么要这样做？

您希望使用最后一个示例，因为这是唯一一个真正参数化的示例。除了安全问题（比你想象的要普遍得多）之外，最好让 ADO.NET 处理参数化，因为如果不检查每个参数，你就无法确定你传入的值是否需要单引号。Type

[编辑]下面是一个示例：

SqlCommand command = new SqlCommand(
    "select foo from bar where baz = @baz",
    yourSqlConnection
);

SqlParameter parameter = new SqlParameter();
parameter.ParameterName = "@baz";
parameter.Value = "xyz";

command.Parameters.Add(parameter);

问题中的示例不会参数化。您需要参数化查询（在某些圈子中是预准备语句）来防止像这样的输入造成损坏：EXEC

';下拉表栏;--

试着把它放在你的变量中（或者不要，如果你重视表）。也可以进行更微妙和破坏性的查询。fuzbar

下面是如何使用 SQL Server 执行参数的示例：Here's an example of how you do parameters with Sql Server：

Public Function GetBarFooByBaz(ByVal Baz As String) As String
    Dim sql As String = "SELECT foo FROM bar WHERE baz= @Baz"

    Using cn As New SqlConnection("Your connection string here"), _
        cmd As New SqlCommand(sql, cn)

        cmd.Parameters.Add("@Baz", SqlDbType.VarChar, 50).Value = Baz
        Return cmd.ExecuteScalar().ToString()
    End Using
End Function

存储过程有时被认为可以防止 SQL 注入。但是，大多数情况下，您仍然必须使用查询参数调用它们，否则它们将无济于事。如果以独占方式使用存储过程，则可以关闭应用程序用户帐户的 SELECT、UPDATE、ALTER、CREATE、DELETE 等权限（除 EXEC 之外的几乎所有权限），并以这种方式获得一些保护。

您的命令文本需要如下所示：

cmdText = "SELECT foo FROM bar WHERE baz = ?"

cmdText = "EXEC foo_from_baz ?"

然后添加参数值。这种方式可确保值 con 最终仅用作值，而使用其他方法时，如果变量 fuz 设置为

"x'; delete from foo where 'a' = 'a"

你能看到会发生什么吗？

大多数人会通过服务器端编程语言库来做到这一点，比如PHP的PDO或Perl DBI。

例如，在 PDO 中：

$dbh=pdo_connect(); //you need a connection function, returns a pdo db connection

$sql='insert into squip values(null,?,?)';

$statement=$dbh->prepare($sql);

$data=array('my user supplied data','more stuff');

$statement->execute($data);

if($statement->rowCount()==1){/*it worked*/}

这负责转义数据以插入数据库。

一个优点是，您可以使用一个准备好的语句多次重复插入，从而获得速度优势。

例如，在上面的查询中，我可以准备一次语句，然后从一堆数据中循环创建数据数组，并根据需要多次重复 ->execute。

绝对是最后一个，即

还是我需要做一些更广泛的事情......？（是的，cmd.Parameters.Add())

参数化查询有两个主要优点：

• 安全性：这是避免SQL注入漏洞的好方法
• 性能：如果定期调用相同的查询，只是使用不同的参数，则参数化查询可能允许数据库缓存查询，这是性能提升的重要来源。
• 额外：您不必担心数据库代码中的日期和时间格式问题。同样，如果您的代码将在具有非英语区域设置的计算机上运行，则不会遇到小数点/小数逗号的问题。

这是一个从 SQL 开始的简短类，您可以从那里构建并添加到类中。

MySQL数据库

Public Class mysql

    'Connection string for mysql
    Public SQLSource As String = "Server=123.456.789.123;userid=someuser;password=somesecurepassword;database=somedefaultdatabase;"

    'database connection classes

    Private DBcon As New MySqlConnection
    Private SQLcmd As MySqlCommand
    Public DBDA As New MySqlDataAdapter
    Public DBDT As New DataTable
    Public BindSource As New BindingSource
    ' parameters
    Public Params As New List(Of MySqlParameter)

    ' some stats
    Public RecordCount As Integer
    Public Exception As String

    Function ExecScalar(SQLQuery As String) As Long
        Dim theID As Long
        DBcon.ConnectionString = SQLSource
        Try
            DBcon.Open()
            SQLcmd = New MySqlCommand(SQLQuery, DBcon)
            'loads params into the query
            Params.ForEach(Sub(p) SQLcmd.Parameters.AddWithValue(p.ParameterName, p.Value))

            'or like this is also good
            'For Each p As MySqlParameter In Params
            ' SQLcmd.Parameters.AddWithValue(p.ParameterName, p.Value)
            ' Next
            ' clears params
            Params.Clear()
            'return the Id of the last insert or result of other query
            theID = Convert.ToInt32(SQLcmd.ExecuteScalar())
            DBcon.Close()

        Catch ex As MySqlException
            Exception = ex.Message
            theID = -1
        Finally
            DBcon.Dispose()
        End Try
        ExecScalar = theID
    End Function

    Sub ExecQuery(SQLQuery As String)

        DBcon.ConnectionString = SQLSource
        Try
            DBcon.Open()
            SQLcmd = New MySqlCommand(SQLQuery, DBcon)
            'loads params into the query
            Params.ForEach(Sub(p) SQLcmd.Parameters.AddWithValue(p.ParameterName, p.Value))

            'or like this is also good
            'For Each p As MySqlParameter In Params
            ' SQLcmd.Parameters.AddWithValue(p.ParameterName, p.Value)
            ' Next
            ' clears params

            Params.Clear()
            DBDA.SelectCommand = SQLcmd
            DBDA.Update(DBDT)
            DBDA.Fill(DBDT)
            BindSource.DataSource = DBDT  ' DBDT will contain your database table with your records
            DBcon.Close()
        Catch ex As MySqlException
            Exception = ex.Message
        Finally
            DBcon.Dispose()
        End Try
    End Sub
    ' add parameters to the list
    Public Sub AddParam(Name As String, Value As Object)
        Dim NewParam As New MySqlParameter(Name, Value)
        Params.Add(NewParam)
    End Sub
End Class

MS SQL/Express

Public Class MSSQLDB
    ' CREATE YOUR DB CONNECTION
    'Change the datasource
    Public SQLSource As String = "Data Source=someserver\sqlexpress;Integrated Security=True"
    Private DBCon As New SqlConnection(SQLSource)

    ' PREPARE DB COMMAND
    Private DBCmd As SqlCommand

    ' DB DATA
    Public DBDA As SqlDataAdapter
    Public DBDT As DataTable

    ' QUERY PARAMETERS
    Public Params As New List(Of SqlParameter)

    ' QUERY STATISTICS
    Public RecordCount As Integer
    Public Exception As String

    Public Sub ExecQuery(Query As String, Optional ByVal RunScalar As Boolean = False, Optional ByRef NewID As Long = -1)
        ' RESET QUERY STATS
        RecordCount = 0
        Exception = ""
        Dim RunScalar As Boolean = False

        Try
            ' OPEN A CONNECTION
            DBCon.Open()

            ' CREATE DB COMMAND
            DBCmd = New SqlCommand(Query, DBCon)

            ' LOAD PARAMS INTO DB COMMAND
            Params.ForEach(Sub(p) DBCmd.Parameters.Add(p))

            ' CLEAR PARAMS LIST
            Params.Clear()

            ' EXECUTE COMMAND & FILL DATATABLE
            If RunScalar = True Then
                NewID = DBCmd.ExecuteScalar()
            End If
            DBDT = New DataTable
            DBDA = New SqlDataAdapter(DBCmd)
            RecordCount = DBDA.Fill(DBDT)
        Catch ex As Exception
            Exception = ex.Message
        End Try


        ' CLOSE YOUR CONNECTION
        If DBCon.State = ConnectionState.Open Then DBCon.Close()
    End Sub

    ' INCLUDE QUERY & COMMAND PARAMETERS
    Public Sub AddParam(Name As String, Value As Object)
        Dim NewParam As New SqlParameter(Name, Value)
        Params.Add(NewParam)
    End Sub
End Class