Trigger 4 - Trigger to prevent duplication of an Account record based on Name whenever a record is inserted or updated.

 Trigger 4 scenario - Trigger to prevent duplication of an Account record based on Name whenever a record is inserted or updated.

trigger AccountTrigger on Account (before insert, before update) { if (Trigger.isBefore) { if (Trigger.isInsert) { AccountTriggerHandler.preventDuplicateNames(Trigger.new, null); } else if (Trigger.isUpdate) { AccountTriggerHandler.preventDuplicateNames(Trigger.new, Trigger.oldMap); } } }

public class AccountTriggerHandler {

    public static void preventDuplicateNames(List<Account> newAccounts, Map<Id, Account> oldAccountMap) {

        Set<String> newAccountNames = new Set<String>();

        List<Account> recordsToValidate = new List<Account>();

        // 1. Isolate the names being added or changed

        for (Account acc : newAccounts) {

            if (acc.Name != null) {

                // If inserting, or updating to a new/different name

                if (oldAccountMap == null || acc.Name != oldAccountMap.get(acc.Id).Name) {

                    newAccountNames.add(acc.Name);

                    recordsToValidate.add(acc);

                }

            }

        }

        // 2. Query existing accounts in the database with these names

        if (!newAccountNames.isEmpty()) {

            Set<String> existingNamesInDb = new Set<String>();

            

            for (Account existingAcc : [SELECT Name FROM Account WHERE Name IN :newAccountNames]) {

                existingNamesInDb.add(existingAcc.Name.toLowerCase());

            }

            // 3. Track duplicates within the same batch (e.g., bulk upload containing duplicates)

            Set<String> namesInCurrentBatch = new Set<String>();

            // 4. Compare and throw error if a match is found

            for (Account acc : recordsToValidate) {

                String currentNameLower = acc.Name.toLowerCase();

                if (existingNamesInDb.contains(currentNameLower) || namesInCurrentBatch.contains(currentNameLower)) {

                    acc.Name.addError('An Account with the name "' + acc.Name + '" already exists.');

                } else {

                    namesInCurrentBatch.add(currentNameLower);

                }

            }

        }

    }

}