Data loading from a database into an application is useful
more so if there will be frequent changes on the data stored in the databases. The
data is loaded from the database when the application is loading. Any changes
on the data are reflected into the grid carrying our data in the application.
I will demonstrate using PHP and ExtJS on how to query a
database and return the data into a JSON format that will be used in our JavaScript
application.
First, we write a script that will query our database in PHP
(data.php)
//data.php
$db = pg_connect("host=somehost port=someport dbname=****
user=**** password=****") or die('could not connect:'.pg_last_error());
$result = pg_query($db, "SELECT *,ST_AsGeoJSON(geom)
FROM Africa") or die("Data load failed:".pg_last_error());
$rows = array(
'type' => 'FeatureCollection',
'features' => array()
);
while($r = pg_fetch_assoc($result))
{
$rows[]
= $r;
}
echo
json_encode($rows);
?>
This will return our result as a JSON file.We then define a
path in our JavaScript file to point to the query results
var mydata = "data.php";
Secondly, we create a JSON store to read our query result
above.This will be done using the ExtJS library Ext.data.JsonStore()
var store = new Ext.data.JsonStore({
proxy:
{
type:
'ajax',
url:mydata,
reader:
{
type:
'json',
}
},
fields:
[
{name:
'gid', type: 'int'},
'cntry_name',
'sovereign', 'pop_cntry','curr_type','landlocked'
]
});
We then load our store with data from mydata
store.load();
Lastly, we define our grid that will display the data
var grid = new Ext.grid.GridPanel({
store:
store,
columns:
[
{header:
'gid', width: 50, sortable: true, dataIndex: 'gid'},
{header:
'Country Name', width: 100, sortable: true, dataIndex: 'cntry_name'},
{header:
'Sovereign', width: 100, sortable: true, dataIndex: 'sovereign'},
{header:
'Population', width: 250, sortable: true, dataIndex: 'pop_cntry'},
{header:
'Currency', width: 250, sortable: true, dataIndex: 'curr_type'},
{header:
'Landlocked', width: 250, sortable: true, dataIndex: 'landlocked'}
],
stripeRows:
true,
columnLines:true,
title:'DB
Grid'
});
The results resembles this;
That was a short demonstration on how data can be loaded
from a PostgreSQL database with PHP into our application and be displayed in a
grid.
There are various ways to achieve this, and this is just one
of them. Hope this helps.