我们可以将之前章节中的代码用来从数据库中读取数据。

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通过PHP Server从MySQL数据库中获取数据

     
 
      
         
        
             
{
   { x.Name }}
             
{
   { x.Country }}
          
       
      
     

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通过ASP.NET Server从MSSQL数据库中获取数据

     
 
      
         
        
             
{
   { x.Name }}
             
{
   { x.Country }}
          
       
      
     

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服务器代码示例

　　下面几小节列出了几种不同的服务器端代码，用来从数据库中获取数据。

　　1. 使用PHP和MySQL。返回JSON数据。

　　2. 使用PHP和MS Access。返回JSON数据。

　　3. 使用ASP.NET，VB和MS Access。返回JSON数据。

　　4. 使用ASP.NET，Razor和SQL Lite。返回JSON数据。

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跨站HTTP请求

　　从不同的服务器请求数据被称为跨站HTTP请求（即cross-site HTTP requests）。

　　跨站HTTP请求在web开发中很普遍。许多页面常常需要从不同的服务器加载各种资源，如CSS，images和scripts等。

　　在现代浏览器中，出于安全考虑，通过脚本进行跨站HTTP请求被严格限制，只允许访问同一站点内的数据。

　　下面这行代码被用在PHP中，用来允许跨站HTTP请求。

header("Access-Control-Allow-Origin: *");

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1. 使用PHP和MySQL

     query("SELECT CompanyName, City, Country FROM Customers");$outp = "";while($rs = $result->fetch_array(MYSQLI_ASSOC)) {    if ($outp != "") {
   $outp .= ",";}    $outp .= '{"Name":"'  . $rs["CompanyName"] . '",';    $outp .= '"City":"'   . $rs["City"]        . '",';    $outp .= '"Country":"'. $rs["Country"]     . '"}'; }$outp ='{"records":['.$outp.']}';$conn->close();echo($outp);?>

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2. 使用PHP和MS Access

     open("PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source=Northwind.mdb");$rs = $conn->execute("SELECT CompanyName, City, Country FROM Customers");$outp = "";while (!$rs->EOF) {    if ($outp != "") {
   $outp .= ",";}    $outp .= '{"Name":"'  . $rs["CompanyName"] . '",';    $outp .= '"City":"'   . $rs["City"]        . '",';    $outp .= '"Country":"'. $rs["Country"]     . '"}';     $rs->MoveNext();}$outp ='{"records":['.$outp.']}';$conn->close();echo ($outp);?>

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3. 使用ASP.NET，VB和MS Access

<%@ Import Namespace="System.IO"%><%@ Import Namespace="System.Data"%><%@ Import Namespace="System.Data.OleDb"%><%Response.AppendHeader("Access-Control-Allow-Origin", "*")Response.AppendHeader("Content-type", "application/json")Dim conn As OleDbConnectionDim objAdapter As OleDbDataAdapterDim objTable As DataTableDim objRow As DataRowDim objDataSet As New DataSet()Dim outpDim cconn = New OledbConnection("Provider=Microsoft.Jet.OLEDB.4.0;data source=Northwind.mdb")objAdapter = New OledbDataAdapter("SELECT CompanyName, City, Country FROM Customers", conn)objAdapter.Fill(objDataSet, "myTable")objTable=objDataSet.Tables("myTable")outp = ""c = chr(34)for each x in objTable.Rowsif outp <> "" then outp = outp & ","outp = outp & "{
    " & c & "Name"    & c & ":" & c & x("CompanyName") & c & ","outp = outp &       c & "City"    & c & ":" & c & x("City")        & c & "," outp = outp &       c & "Country" & c & ":" & c & x("Country")     & c & "}"nextoutp ="{
    " & c & "records" & c & ":[" & outp & "]}"response.write(outp)conn.close%>

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4. 使用ASP.NET，Razor和SQL Lite

@{Response.AppendHeader("Access-Control-Allow-Origin", "*")Response.AppendHeader("Content-type", "application/json")var db = Database.Open("Northwind");var query = db.Query("SELECT CompanyName, City, Country FROM Customers");var outp =""var c = chr(34)}@foreach(var row in query){if outp <> "" then outp = outp + ","outp = outp + "{
    " + c + "Name"    + c + ":" + c + @row.CompanyName + c + ","outp = outp +       c + "City"    + c + ":" + c + @row.City        + c + ","outp = outp +       c + "Country" + c + ":" + c + @row.Country     + c + "}"}outp ="{
    " + c + "records" + c + ":[" + outp + "]}"@outp