Calling SOQL Query from JavaScript in Salesforce

{!REQUIRESCRIPT("/soap/ajax/19.0/connection.js")}
var url = parent.location.href;
try
{
var qr = sforce.connection.query("SELECT id,name FROM Account ");
}
catch (error)
{
alert(error.faultstring);
}

if (qr.size == 0)
{
alert("No Record Existing For updating the records.");
}
else
{
for (var i=0;i<qr.records.length;i++) { alert(qr.records[i].Name); }  }