How to query records from sObject for 50000+ records?

There two more methods to query data more then 50000

Method 1: Use Visualforce page with readOnly attribute set to true
Controller class:

public class StatsController {
public Integer numberOfContacts {
get {
if (numberOfContacts == null) {
numberOfContacts = [select count() from Contact];
}
return numberOfContacts;
}
private set;
}
}
Visualforce page:

<apex:page controller=”StatsController” readOnly=”true”>
<p>Number of Contacts: {!numberOfContacts}</p>
</apex:page>

Method 2: Make a http request using the REST API
HttpRequest req = new HttpRequest();
req.setEndpoint(‘https://’+URL.getSalesforceBaseUrl().getHost()+’/services/data/v20.0/query/?q=SELECT+Id+from+Contact’);
req.setMethod(‘GET’);

string autho = ‘Bearer ‘+ userInfo.getsessionId();
req.setHeader(‘Authorization’, autho);

Http http = new Http();
HTTPResponse res = http.send(req);
string response = res.getBody();
string total = response.substring(response.indexOf(‘totalSize”:’) + 11, response.indexOf(‘,’));
system.debug(‘Total: ‘+ total);

Hi,

You can use Batchable class:

public class ContactBatchable implements Database.Batchable<sObject>, Database.Stateful {
Integer total = 0;

public Database.QueryLocator start(Database.BatchableContext BC){
return Database.getQueryLocator(‘select Id from Contact’);
}

public void execute(
Database.BatchableContext BC,
List<sObject> scope){
total += scope.size();
}

public void finish(Database.BatchableContext BC){
System.debug(‘total: ‘ + total);
}
}

And then execute the following statement in developer console:

Database.executeBatch(new ContactBatchable(), 2000);

Thanks.