ADO世界之SECOND

一、ADO 排序记录

1.对数据进行排序

2.根据指定的字段名处对记录进行升序排序

3.根据指定的字段名处对记录进行降序排序

4.让用户来选择根据哪列进行排序

二、ADO 添加记录

1.向数据库中的表添加记录

2.使用 INSERT command 命令时的注意事项

3.无数据字段

三、ADO 更新记录

1.更新数据库表中的记录

一、ADO 排序记录

使用SQL来规定如何对记录集中的数据进行排序。

1.对数据进行排序

显示 "Customers" 表中的"Companyname"和"Contactname"字段，并根据"Companyname"进行排序（请记得用.asp为后缀保存）：

<html>

<body>

<%

set conn=Server.CreateObject("ADODB.Connection")

conn.Provider="Microsoft.Jet.OLEDB.4.0"

conn.Open "c:/webdata/northwind.mdb"

set rs = Server.CreateObject("ADODB.recordset")

sql="SELECT Companyname, Contactname FROM

Customers ORDER BY CompanyName"

rs.Open sql, conn

%>

<table border="1" width="100%">

  <tr>

  <%for each x in rs.Fields

    response.write("<th>" & x.name & "</th>")

  next%>

  </tr>

  <%do until rs.EOF%>

    <tr>

    <%for each x in rs.Fields%>

      <td><%Response.Write(x.value)%></td>

    <%next

    rs.MoveNext%>

    </tr>

  <%loop

  rs.close

  conn.close%>

</table>

</body>

</html>

2.根据指定的字段名处对记录进行升序排序

<html>

<body>

<%

set conn=Server.CreateObject("ADODB.Connection")

conn.Provider="Microsoft.Jet.OLEDB.4.0"

conn.Open(Server.Mappath("/db/northwind.mdb"))

set rs = Server.CreateObject("ADODB.recordset")

sql="SELECT Companyname, Contactname FROM Customers ORDER BY CompanyName"

rs.Open sql, conn

%>

<table border="1" width="100%">

<tr>

<%for each x in rs.Fields

    response.write("<th>" & x.name & "</th>")

next%>

</tr>

<%do until rs.EOF%>

    <tr>

    <%for each x in rs.Fields%>

       <td><%Response.Write(x.value)%></td>

    <%next

    rs.MoveNext%>

    </tr>

<%loop

rs.close

conn.close

%>

</table>

</body>

</html>

3.根据指定的字段名处对记录进行降序排序

<html>

<body>

<%

set conn=Server.CreateObject("ADODB.Connection")

conn.Provider="Microsoft.Jet.OLEDB.4.0"

conn.Open(Server.Mappath("/db/northwind.mdb"))

set rs = Server.CreateObject("ADODB.recordset")

sql="SELECT Companyname, Contactname FROM Customers ORDER BY CompanyName DESC"

rs.Open sql, conn

%>

<table border="1" width="100%">

<tr>

<%for each x in rs.Fields

    response.write("<th>" & x.name & "</th>")

next%>

</tr>

<%do until rs.EOF%>

    <tr>

    <%for each x in rs.Fields%>

       <td><%Response.Write(x.value)%> </td>

    <%next

    rs.MoveNext%>

    </tr>

<%loop

rs.close

conn.close

%>

</table>

</body>

</html>

4.让用户来选择根据哪列进行排序

<html>

<body>

<table border="1" width="100%" bgcolor="#fff5ee">

<tr>

<th align="left" bgcolor="#b0c4de">

<a href="/example/adoe/demo_adoe_sort_3.asp?sort=companyname">Company</a>

</th>

<th align="left" bgcolor="#b0c4de">

<a href="/example/adoe/demo_adoe_sort_3.asp?sort=contactname">Contact</a>

</th>

</tr>

<%

if request.querystring("sort")<>"" then

   sort=request.querystring("sort")

else

   sort="companyname"

end if

set conn=Server.CreateObject("ADODB.Connection")

conn.Provider="Microsoft.Jet.OLEDB.4.0"

conn.Open(Server.Mappath("/db/northwind.mdb"))

set rs=Server.CreateObject("ADODB.recordset")

sql="SELECT Companyname,Contactname FROM Customers ORDER BY " & sort

rs.Open sql,conn

do until rs.EOF

   response.write("<tr>")

   for each x in rs.Fields

     response.write("<td>" & x.value & "</td>")

   next

   rs.MoveNext

   response.write("</tr>")

loop

rs.close

conn.close

%>

</table>

</body>

</html>

二、ADO 添加记录

使用 SQL 的 INSERT INTO 命令向数据库中的表添加记录。

1.向数据库中的表添加记录

向 Northwind 数据库中的 Customers 表添加一条新的记录。

首先要创建一个表单，这个表单包含了从中搜集数据的输入域：

<html>

<body>

<form method="post" action="demo_add.asp">

<table>

<tr>

<td>CustomerID:</td>

<td><input name="custid"></td>

</tr><tr>

<td>Company Name:</td>

<td><input name="compname"></td>

</tr><tr>

<td>Contact Name:</td>

<td><input name="contname"></td>

</tr><tr>

<td>Address:</td>

<td><input name="address"></td>

</tr><tr>

<td>City:</td>

<td><input name="city"></td>

</tr><tr>

<td>Postal Code:</td>

<td><input name="postcode"></td>

</tr><tr>

<td>Country:</td>

<td><input name="country"></td>

</tr>

</table>

<br /><br />

<input type="submit" value="Add New">

<input type="reset" value="Cancel">

</form>

</body>

</html>

当用户按下确认按钮时，这个表单就会被送往名为 "demo_add.asp" 的文件。文件 "demo_add.asp" 中含有可向 Customers 表添加一条新记录的代码：

<html>

<body>

<%

set conn=Server.CreateObject("ADODB.Connection")

conn.Provider="Microsoft.Jet.OLEDB.4.0"

conn.Open "c:/webdata/northwind.mdb"

sql="INSERT INTO customers (customerID,companyname,"

sql=sql & "contactname,address,city,postalcode,country)"

sql=sql & " VALUES "

sql=sql & "('" & Request.Form("custid") & "',"

sql=sql & "'" & Request.Form("compname") & "',"

sql=sql & "'" & Request.Form("contname") & "',"

sql=sql & "'" & Request.Form("address") & "',"

sql=sql & "'" & Request.Form("city") & "',"

sql=sql & "'" & Request.Form("postcode") & "',"

sql=sql & "'" & Request.Form("country") & "')"

on error resume next

conn.Execute sql,recaffected

if err<>0 then

Response.Write("No update permissions!")

else

Response.Write("<h3>" & recaffected & " record added</h3>")

end if

conn.close

%>

</body>

</html>

2.使用 INSERT command 命令时的注意事项

1.如果表含有一个主键，请确保向主键字段添加的值是唯一且非空的（否则，provider 就不会追加此记录，亦或发生错误）

2.如果表含有一个自动编号的字段，请不要在 INSERT 命令中涉及此字段（这个字段的值是由 provider 负责的）

3.无数据字段

在 MS Access 数据库中，将 AllowZeroLength 属性设置为 “Yes”，就可以在文本、超链接以及备忘字段输入零长度的字符串 ("")。

注：并非所有的数据库都支持零长度的字符串。

三、ADO 更新记录

使用 SQL 的 UPDATE 来更新数据库表中的某条记录。

1.更新数据库表中的记录

更新 Northwind 数据中 Customers 表的某条记录。

首先创建一个表格，来列出 Customers 中的所有记录。

<html>

<body>

<%

set conn=Server.CreateObject("ADODB.Connection")

conn.Provider="Microsoft.Jet.OLEDB.4.0"

conn.Open "c:/webdata/northwind.mdb"

set rs=Server.CreateObject("ADODB.Recordset")

rs.open "SELECT * FROM customers",conn

%>

<h2>List Database</h2>

<table border="1" width="100%">

<tr>

<%

for each x in rs.Fields

  response.write("<th>" & ucase(x.name) & "</th>")

next

%>

</tr>

<% do until rs.EOF %>

<tr>

<form method="post" action="demo_update.asp">

<%

for each x in rs.Fields

  if lcase(x.name)="customerid" then%>

    <td>

    <input type="submit" name="customerID" value="<%=x.value%>">

    </td>

  <%else%>

    <td><%Response.Write(x.value)%></td>

  <%end if

next

%>

</form>

<%rs.MoveNext%>

</tr>

<%

loop

conn.close

%>

</table>

</body>

</html>

如果用户点击 "customerID" 列中的按钮，会打开一个新文件 "demo_update.asp"。此文件包含了创建输入域的源代码，这些输入域基于数据库中记录的字段，同时也含有一个保存修改的“更新按钮”：

<html>

<body>

<h2>Update Record</h2>

<%

set conn=Server.CreateObject("ADODB.Connection")

conn.Provider="Microsoft.Jet.OLEDB.4.0"

conn.Open "c:/webdata/northwind.mdb"

cid=Request.Form("customerID")

if Request.form("companyname")="" then

  set rs=Server.CreateObject("ADODB.Recordset")

  rs.open "SELECT * FROM customers WHERE customerID='" & cid & "'",conn

  %>

  <form method="post" action="demo_update.asp">

  <table>

  <%for each x in rs.Fields%>

  <tr>

  <td><%=x.name%></td>

  <td><input name="<%=x.name%>" value="<%=x.value%>"></td>

  <%next%>

  </tr>

  </table>

  <br /><br />

  <input type="submit" value="Update record">

  </form>

<%

else

  sql="UPDATE customers SET "

  sql=sql & "companyname='" & Request.Form("companyname") & "',"

  sql=sql & "contactname='" & Request.Form("contactname") & "',"

  sql=sql & "address='" & Request.Form("address") & "',"

  sql=sql & "city='" & Request.Form("city") & "',"

  sql=sql & "postalcode='" & Request.Form("postalcode") & "',"

  sql=sql & "country='" & Request.Form("country") & "'"

  sql=sql & " WHERE customerID='" & cid & "'"

  on error resume next

  conn.Execute sql

  if err<>0 then

    response.write("No update permissions!")

  else

    response.write("Record " & cid & " was updated!")

  end if

end if

conn.close

%>

</body>

</html>