网络构建 - SQL获取数据

从头开始建立第九部分网站：使用SQL读取数据。

我们将要做什么

在本章中，我们将：

创建服务器页面

服务器运行PHP和MySQL

<?php
header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");

$conn = new mysqli("myServer", "myUser", "myPassword", "Northwind");

$result = $conn->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);
?>

跨站点HTTP请求

从不同的服务器请求数据（而不是请求页），被称为跨站点的HTTP请求。

跨站点请求是在网络上非常普遍。Many pages load css, images, or scripts from different servers. 许多网页加载CSS，图像或脚本来自不同的服务器。

在现代浏览器， 从脚本跨站点的HTTP请求被限制在同一站点出于安全原因。

下面的线，在上面的PHP示例，已添加到允许跨站点访问的页面。

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

服务器运行PHP和MS Access

<?php
header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=ISO-8859-1");

$conn = new COM("ADODB.Connection");
$conn->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);
?>

服务器运行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 OleDbConnection
Dim objAdapter As OleDbDataAdapter
Dim objTable As DataTable
Dim objRow As DataRow
Dim objDataSet As New DataSet()
Dim outp
Dim c
conn = 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.Rows
if 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 & "}"
next
outp ="{" & c & "records" & c & ":[" & outp & "]}"

conn.close
response.write(outp)
%>

服务器运行ASP.NET，剃刀和SQL精简版

@{
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

网站建设