Encoding form data for SQL Server input and output to HTML

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Summary

When you are working with records in a database using Microsoft Active Server Pages (ASP) for Internet Information Services (IIS), errors may occur when the text has not been properly formatted for creating a SQL Server clause.

For example, when you create an ASP page to store information posted from an HTML form to a database, you may see an error message similar to the following:
Microsoft OLE DB Provider for ODBC Drivers (0x80040E14)
[Microsoft][ODBC Microsoft Access Driver] Syntax error (missing operator) in query expression '<SQL Text>'.
/<path>/<filename.asp>, line <nnn>

More Information

The error message above occurs when you try to submit a name with an apostrophe, (for example "O'Malley"), and then insert that name into a SQL Server clause without first "escaping" it. This can result in a SQL Server clause that resembles the following:
INSERT INTO Table (txtName VALUES ('O'Malley')
Because SQL Server uses the apostrophe as a text delimiter, the apostrophe in the name inadvertently signifies an end to the data, which causes the error message to occur. This text can be "escaped" by using two apostrophes, for example:
INSERT INTO Table (txtName VALUES ('O''Malley')
Obviously, it is not ideal to mandate that all users on a Web site enter two apostrophes for each desired apostrophe. In addition, when text is later extracted from a database, certain formatting characters are ignored during HTML parsing on a client (for example CR-LF, TAB, and so on.)


An ASP solution

The following ASP code defines two functions that are designed to handle some simple parsing of information for input/output of SQL Server data, and can easily be expanded to incorporate more functionality:
  • FixForSQL() parses a string for input to SQL Server
      Function FixForSQL(tmpText1)
    ' define a working variable
    Dim tmpText2
    ' populate our working variable
    tmpText2 = tmpText1
    ' compact a CR-LF sequence as CR to save space
    tmpText2 = Replace(tmpText1,vbCrLf,Chr(13))
    ' replace each apostrophe with two apostrophes
    tmpText2 = Replace(tmpText2,Chr(39),String(2,39))
    ' return the fixed string
    FixForSQL = tmpText2
    End Function
  • FixForHTML() parses a string for output to HTML
      Function FixForHTML(tmpText1)
    ' define a working variable
    Dim tmpText2
    ' populate our working variable
    tmpText2 = tmpText1
    ' replace each CR with a line break tag and CR-LF
    tmpText2 = Replace(tmpText2,Chr(13),"<br>" & vbCrLf)
    ' replace each TAB character with four non-breaking space tags
    tmpText2 = Replace(tmpText2,Chr(9),"&#xa0;&#xa0;&#xa0;&#xa0;")
    ' return the fixed string
    FixForHTML = tmpText2
    End Function

Practical example - Guestbook application

The following steps demonstrate how to use the above functions to create a simple guestbook application using ASP and a Microsoft Access database:

  1. Copy the following ASP code and save it to a folder in your Web site with at least IIS script access enabled and Copy the following ASP code and save it to a folder in your Web site with at least IIS "script" access enabled and Everyone - Change NTFS permissions:
    <% @Language="VBScript" %>
    <%
    Option Explicit

    ' define our variables
    Dim strMethod
    Dim strURL
    Dim strTitle
    Dim strSQL
    Dim objCN
    Dim objRS

    ' get some environment variables
    With Request
    strMethod = UCase(.ServerVariables("REQUEST_METHOD"))
    strTitle = UCase(.ServerVariables("SERVER_NAME")) & " Guestbook"
    strURL = LCase(.ServerVariables("URL"))
    End With

    ' open our database connection
    Set objCN = Server.CreateObject("ADODB.Connection")
    objCN.Open "driver={Microsoft Access Driver (*.mdb)};uid=admin;pwd=;" & _
    "dbq=" & Server.MapPath(".\guestbook.mdb")

    ' if the request was a POST then a guest submitted
    If strMethod = "POST" Then
    Dim strName, strComments
    ' get the form data and format it
    strName = FixForSQL(Request.Form("txtName"))
    strComments = FixForSQL(Request.Form("txtComments"))
    ' build the SQL string
    strSQL = "INSERT INTO tblGuestbook (txtName, txtComments)"
    strSQL = strSQL & " VALUES ('" & strName & "','" & strComments & "')"
    ' execute the SQL
    objCN.Execute(strSQL)
    End If

    ' create a SQL string to read all guest entries
    strSQL = "SELECT * FROM tblGuestbook"
    Set objRS = objCN.Execute(strSQL)

    %>
    <html>
    <head><title><%=strTitle%></title></head>
    <body>

    <h1><%=strTitle%></h1>

    <%
    ' only show the guestbook when there are entries
    If Not objRS.EOF Then
    %>

    <table border="1">
    <tr>
    <th>Name</th>
    <th>Comments</th>
    </tr>
    <%
    ' loop through the database
    While Not objRS.EOF
    With Response
    .Write "<tr>" & vbCrLf
    .Write "<td>" & FixForHTML(objRS("txtName")) & "</td>" & vbCrLf
    .Write "<td>" & FixForHTML(objRS("txtComments")) & "</td>" & vbCrLf
    .Write "</tr>" & vbCrLf
    End With
    objRS.MoveNext
    Wend
    %>
    </table>

    <% End If %>

    <form action="<%=strURL%>" method="POST">
    <table>
    <tr>
    <td>Name</td>
    <td><input type="text" name="txtName"><br>
    </tr>
    <tr>
    <td>Comments</td>
    <td><textarea name="txtComments"></textarea><br>
    </tr>
    <tr>
    <td colspan="2"><input type="submit" value="Submit Comments">
    </tr>
    </form>

    </body>
    </html>
    <%
    Function FixForSQL(tmpText1)
    Dim tmpText2
    tmpText2 = tmpText1
    tmpText2 = Replace(tmpText1,vbCrLf,Chr(13))
    tmpText2 = Replace(tmpText2,Chr(39),String(2,39))
    FixForSQL = tmpText2
    End Function

    Function FixForHTML(tmpText1)
    Dim tmpText2
    tmpText2 = tmpText1
    tmpText2 = Replace(tmpText2,Chr(13),"<br>" & vbCrLf)
    tmpText2 = Replace(tmpText2,Chr(9),"&#xa0;&#xa0;&#xa0;&#xa0;")
    FixForHTML = tmpText2
    End Function
    %>
  2. Open Microsoft Access, create a new database, and then save it as Guestbook.mdb in the same folder as the above ASP page. Create a new table in the database named tblGuestbook with the following fields:
    Field NameData TypeField Size
    txtNameText50
    txtCommentsMemoN/A
    Save the table to the database, and then close Microsoft Access.
Testing the Guestbook Application
  1. When you browse the page for the first time, no data is displayed. When information has been submitted, any guestbook entries will appear. Entering apostrophes in names (for example O'Brien, O'Sullivan, and so on) or contractions (such as don't, can't, and so on) are properly formatted and stored in the database.
  2. When information has been submitted, any guestbook entries will appear. Entering apostrophes in names (for example O'Brien, O'Sullivan, and so on) or contractions (such as don't, can't, and so on) are properly formatted and stored in the database.
  3. Entering apostrophes in names (for example O'Brien, O'Sullivan, and so on) or contractions (such as don't, can't, and so on) are properly formatted and stored in the database.

References

Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific requirements.

For more information about Microsoft scripting technologies, visit the Microsoft Developer Network web site:
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ID članka: 246069 - posljednja izmjena: 19. lip 2014. - verzija: 1

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