Practical Examples

Example 1: Updating Account Status Based on Open Opportunities

Let’s say you want to mark accounts as “Has Open Opportunities” if they currently have any open deals.

global class AccountStatusBatch implements Database.Batchable, Database.Stateful {

    // Member variable to track processed account IDs (demonstrates stateful processing)
    private Set<Id> accountsWithOpenOpportunities = new Set<Id>();

    // 1. Start method: Query the records to process
    global Database.QueryLocator start(Database.BatchableContext bc) {
        // Query for Accounts that have at least one open opportunity
        return Database.getQueryLocator('SELECT Id, Name FROM Account WHERE Id IN (SELECT AccountId FROM Opportunity WHERE StageName != \'Closed Won\' AND StageName != \'Closed Lost\')');
    }

    // 2. Execute method: Process each batch of records
    global void execute(Database.BatchableContext bc, List<Account> scope) {
        List<Account> accountsToUpdate = new List<Account>();

        for (Account acc : scope) {
            // In a real-world scenario, you'd re-query opportunities here or join in SOQL
            // For simplicity, we assume the start query is sufficient or that we've
            // already determined this in the start method.
            // If we need to confirm within execute:
            List<Opportunity> openOpps = [SELECT Id FROM Opportunity WHERE AccountId = :acc.Id AND StageName != 'Closed Won' AND StageName != 'Closed Lost'];

            if (!openOpps.isEmpty()) {
                acc.Status__c = 'Has Open Opportunities'; // Assuming a custom field Status__c
                accountsToUpdate.add(acc);
                accountsWithOpenOpportunities.add(acc.Id); // Add to our stateful set
            }
            // Optionally, you could reset the status if no open opportunities
            // else {
            //     acc.Status__c = 'No Open Opportunities';
            //     accountsToUpdate.add(acc);
            // }
        }

        if (!accountsToUpdate.isEmpty()) {
            try {
                update accountsToUpdate;
                System.debug('Updated ' + accountsToUpdate.size() + ' accounts.');
            } catch (DmlException e) {
                // Handle DML exceptions
                System.debug('Error updating accounts: ' + e.getMessage());
            }
        }
    }

    // 3. Finish method: Executed after all batches are processed
    global void finish(Database.BatchableContext bc) {
        // You could send an email notification here
        String message = 'Account Status Batch Job Completed. Processed and potentially updated ' + accountsWithOpenOpportunities.size() + ' accounts with open opportunities.';
        System.debug(message);

        // Example: Send an email to the administrator
        Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
        mail.setSubject('Account Status Batch Job Finished');
        mail.setToAddresses(new List<String>{UserInfo.getUserEmail()}); // Send to current user's email
        mail.setPlainTextBody(message);
        Messaging.sendEmail(new List<Messaging.SingleEmailMessage>{mail});
    }
}

            

How to execute this batch:

AccountStatusBatch batchJob = new AccountStatusBatch();
Id jobId = Database.executeBatch(batchJob, 50); // Execute with a batch size of 50
System.debug('Batch Job ID: ' + jobId);

            

Example 2: Deleting Old Lead Records

This batch removes leads that were created more than a year ago and have no associated open tasks.

global class DeleteOldLeadsBatch implements Database.Batchable<sObject> {

    // Start method: Query leads older than 365 days with no open tasks
    global Database.QueryLocator start(Database.BatchableContext bc) {
        Date oneYearAgo = Date.today().addDays(-365);
        // Subquery to find leads with open tasks
        Set<Id> leadsWithOpenTasks = new Set<Id>();
        for(Task t : [SELECT WhatId FROM Task WHERE What.Type = 'Lead' AND Status != 'Completed' AND CreatedDate >= :oneYearAgo]) {
            leadsWithOpenTasks.add(t.WhatId);
        }

        String query = 'SELECT Id, Name, CreatedDate FROM Lead WHERE CreatedDate < :oneYearAgo';
        if (!leadsWithOpenTasks.isEmpty()) {
            query += ' AND Id NOT IN :leadsWithOpenTasks';
        }
        return Database.getQueryLocator(query);
    }

    // Execute method: Delete each batch of leads
    global void execute(Database.BatchableContext bc, List<Lead> scope) {
        try {
            if (!scope.isEmpty()) {
                delete scope;
                System.debug('Deleted ' + scope.size() + ' old leads.');
            }
        } catch (DmlException e) {
            // Handle DML exceptions
            System.debug('Error deleting leads: ' + e.getMessage());
            // You might want to log these errors more robustly
        }
    }

    // Finish method: Notify completion
    global void finish(Database.BatchableContext bc) {
        String message = 'Old Lead Deletion Batch Job Completed.';
        System.debug(message);
        // Optionally send an email
    }
}

            

How to execute this batch:

DeleteOldLeadsBatch deleteBatch = new DeleteOldLeadsBatch();
Id jobId = Database.executeBatch(deleteBatch, 200); // Execute with a batch size of 200 (default)
System.debug('Delete Old Leads Batch Job ID: ' + jobId);