Write Apex Trigger Whenever a Contact is Inserted / Updated / Deleted, We need to Count child Contacts related to each Account Based on MailingCountry Only for these 4 countries (India, USA, England, Japan) Then store the count on Account object.

Write Apex Trigger Whenever a Contact is Inserted / Updated / Deleted, We need to Count child Contacts related to each Account Based on MailingCountry Only for these 4 countries (India, USA, England, Japan) Then store the count on Account object.

Create Custom Fields on Account

Create 4 Number fields on Account:

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Field Label	API Name
India Contacts Count	India_Contacts__c
USA Contacts Count	USA_Contacts__c
England Contacts Count	England_Contacts__c
Japan Contacts Count	Japan_Contacts__c

Data Type → Number (0 Decimal Places)

Logic Approach (Best Practice – Bulkified)

Use after insert
Use after update
Use after delete
Use after undelete
Collect all AccountIds
Run Aggregate Query
Update Account

Step 1 Account Trigger (After Update): ContactPracticeTrigger.apxt

   TRIGGER AggregateResultContactPractice ON Contact (BEFORE INSERT, after INSERT, BEFORE UPDATE, after UPDATE, BEFORE DELETE, after DELETE, after undelete) {

```
 
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  //COUNT child Contacts related TO each Account Based ON MailingCountry ONLY FOR these 4 countries:India, USA, England, AND Japan

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    //THEN store the COUNT ON Account object: India_Contacts__c, USA_Contacts__c, England_Contacts__c, Japan_Contacts__c

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    IF(TRIGGER.isAfter){
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           Set<Id> accountIds = NEW Set<Id>();

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            IF(TRIGGER.isInsert || TRIGGER.isUpdate || TRIGGER.isUndelete){

                FOR(Contact con:TRIGGER.new){

                    IF(con.AccountId != NULL){

                        accountIds.add(con.AccountId);

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                    }
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                }
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            }
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            IF(TRIGGER.isDelete || TRIGGER.isUpdate ){

                FOR(Contact con2:TRIGGER.old){

                    IF(con2.AccountId != NULL){

                        accountIds.add(con2.AccountId);

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                    }
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                }
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            }
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         List<AggregateResult> agrList = [SELECT AccountId, MailingCountry, COUNT(Id) totalCount FROM Contact WHERE AccountId IN:accountIds AND MailingCountry IN ('India','USA','England','Japan') GROUP BY AccountId, MailingCountry ];

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```

          Map<Id, Integer> IndiaMap = NEW Map<Id, Integer>();

          Map<Id, Integer> UsaMap = NEW Map<Id, Integer>();

          Map<Id, Integer> EnglandMap = NEW Map<Id, Integer>();

          Map<Id, Integer> JapanMap = NEW Map<Id, Integer>();

```
 
```

            FOR(AggregateResult ar:agrList){

               Id ids = (Id) ar.get('AccountId');

               String country = (String) ar.get('MailingCountry');

               INTEGER countValue = (INTEGER) ar.get('totalCount');

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```
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                IF(country == 'India'){
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                    IndiaMap.put(ids, countValue);

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                } 
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                ELSE IF (country == 'USA'){

                    UsaMap.put(ids, countValue);

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                }
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                ELSE IF (country == 'England'){

                    EnglandMap.put(ids, countValue);

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                }
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                ELSE IF (country == 'Japan'){

                    JapanMap.put(ids, countValue);

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                }
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            }
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```

            List<Account> accItem = NEW List<Account>();

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```

            FOR(Id accId:accountIds){

                Account accObj = NEW Account();

                accObj.India_Contacts__c = IndiaMap.get(accId);

                accObj.USA_Contacts__c = UsaMap.get(accId);

                accObj.England_Contacts__c = EnglandMap.get(accId);

                accObj.Japan_Contacts__c = JapanMap.get(accId);

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                accObj.Id = accId;
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```
                accItem.add(accObj);
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            }
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            IF(!accItem.isEmpty()){
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                UPDATE accItem;
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            }
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    }
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}
```

How This Works (Step-by-Step):

Collect Account IDs from Trigger context
Run one Aggregate SOQL query
Group by AccountId and MailingCountry
Store result in Map
Update Account with country-wise count
If no contacts → set count = 0

Why This is Interview-Ready?:

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Fully Bulkified
Uses Aggregate Query
Handles Insert/Update/Delete/Undelete
No SOQL inside loop
No DML inside loop

Further post that would you like to learn in Salesforce

FAQ (Frequently Asked Questions)

Can a contact be associated with multiple accounts in Salesforce?

Enabling Account Contact Relationship access mapping feature allows your sales reps to easily track the relationships between the customers and businesses they work with. It's quick to set up and allow reps to relate a single contact record to multiple accounts.

How are contacts and accounts related in Salesforce?

The relationship rules are still simple. Every contact needs to be directly associated with an account. This is the account that appears in Account Name and is usually the company the contact is most closely associated with. Any other accounts associated with the contact represent indirect relationships.

What happens to related records when you merge accounts in Salesforce?

What happens to related records when accounts are merged? All related records—contacts, opportunities, cases—are automatically transferred to the master account. Note that conflicting fields require manual selection of which data to retain.

Vijay Kumar

Hi, This is Vijay Kumar behind the admin and founder of w3web.net. I am a senior software developer and working in MNC company from more than 8 years. I am great fan of technology, configuration, customization & development. Apart of this, I love to write about Blogging in spare time, Working on Mobile & Web application development, Salesforce lightning, Salesforce LWC and Salesforce Integration development in full time. [Read full bio] | | The Sitemap where you can find all published post on w3web.net

Can a contact be associated with multiple accounts in Salesforce?

How are contacts and accounts related in Salesforce?

What happens to related records when you merge accounts in Salesforce?

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Vijay Kumar