Rdbhost.com now provides JSONP as a format option.
JSONP allows data to be requested from a site different from that of the referencing page. You can put a page on your domain somewhere, and retrieve data from www.rdbhost.com using a cross-site request and the JSONP format.
Let us look at a very simple example. Rdbhost maintains a table of performance statistics (on itself, about itself) in a table 'stats' in account db000000005 . We will query that table from our page for a count of records. The entire example page is 11 lines:
Lines 01 to 03 are just html to show the count when we get it. Lines 05 to 07 are a javascript function to process the count data after receiving it, and line 09 is the actual request.
01 <html>
02 <body>
03 Count of records in 'stats': <span id="count"></span>
04 <script>
05 function showct(data){
06 document.getElementById("count").innerHTML = data['records']['rows'][0]["count"];
07 };
08 </script>
09 <script src="http://www.rdbhost.com/db/r0000000005?q=SELECT%20count(*)%20from%20stats&callback=showct"></script>
10 </body>
11 </html>
Line 09 is a script tag: it retrieves the page at the url identified in 'src', and processes it as a script. The 'callback' parameter indicates the name to 'wrap' around the data, and implies the request needs JSONP output format. The content received is this:
When this is processed as a script, the 'showct(...)' is interpreted as a function call, and executed. The function had been defined in lines 05 to 07, and just extracted the 'count' element of the JSON and put it in the HTML element 'count', for display.
showct({
"records": {
"header": {
"count": 20
},
"rows": [
{
"count": "5456"
}
]
},
"row_count": [
1,
"1 Rows Affected"
],
"status": [
"complete",
"OK"
]
})
When this is processed as a script, the 'showct(...)' is interpreted as a function call, and executed. The function had been defined in lines 05 to 07, and just extracted the 'count' element of the JSON and put it in the HTML element 'count', for display.
This page works cross-site, so you could host such a page on your site, under your domain, and retrieve records from rdbhost.com dynamically. If you prefer jQuery, you can retrieve JSONP content using the .getJSON function, including a 'callback' parameter in the url to retrieve. Using jQuery has the virtue that you do not need a named callback function, as jQuery will allow its typical anonymous callbacks even with JSONP.
Limitations:
- Requests use 'GET' mode, not 'POST', so any authentication information would be there in the link for users to read.
- Rdbhost does not permit authcodes to be passed in GET requests, for security reasons. JSONP usage is thus only useful for queries using the 'r' role, with no authentication. To query your own account, you would need to enable the 'r' role from the profile page, and probably GRANT it some SELECT privileges on tables in the account, using rdbadmin or the SQL_form.
The request urls can easily get long enough to be unwieldy. These two pages demonstrate a technique for putting the url in a javascript variable, where it can be line-wrapped.
The Rdbhost website itself is at: http://www.rdbhost.com.
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