#Apex48 人がディスカッション中

Hi @Rohit ., 

acc.Contacts is available because the query uses a Parent-to-Child Relationship Query:

SELECT Id, Name,       (SELECT Id, Name, Department FROM Contacts)FROM Account

The child Contacts are retrieved as part of the same SOQL query and stored in the acc.Contacts relationship collection. Therefore, no separate SOQL query is required inside the loop. 

Regarding a large number of Contacts, the nested loop is valid, but retrieving every Contact just to count IT Contacts may be inefficient. If we only need the count, an Aggregate SOQL query

 with COUNT() and GROUP BY AccountId would be more efficient because the database performs the counting instead of Apex. 

So, use the relationship query when you need to process Contact records; use Aggregate SOQL when you only need counts/statistics

.  

Hope this help !!.

Hi @Pranjal Budhlakoti, 

 A single SOQL query outside the loop is faster and follows Apex best practices. SOQL inside a loop can quickly hit the SOQL governor limit. 

Similarly, performing DML one-by-one inside a loop is not recommended. For 200 records, it can consume 200 DML statements and exceed the 150 DML statement limit. 

The best approach is to query records once, process them in a loop, and perform DML once using a List. This makes the code bulkified and governor-limit safe.  

Thank You.

@Hitesh SharmaHitesh, for a beginner I recommend this roadmap:

Apex Basics → Variables/Conditions/Loops → List/Set/Map → sObjects → SOQL → DML → Classes → Exceptions → Governor Limits & Bulkification → Triggers → Test Classes → Async Apex → REST/Callouts.

Start with the official Trailhead Quick Start: Apex, then Apex Basics & Database. Trailhead Quick Start: Apex Apex Basics & Database

For reference, use the official Apex Developer Guide. 

@Himanshu Shekhar Yes, you can declare the List in the main Apex class itself.

For example:

public class NewConstEx {
    public List<String> subjects = new List<String>{
        'Apex',
        'LWC',
        'JS',
        'Java'
    };
    public NewConstEx() {
    }
}

Then Anonymous Window:

NewConstEx N = new NewConstEx();
System.debug(N.subjects);

Your original approach is also correct:

List<String> mysubject = new List<String>{'Apex', 'LWC', 'JS', 'Java'};
NewConstEx N = new NewConstEx(mysubject);

Constructor is useful when you want to pass different Lists/values from outside. If the List is always fixed, you can initialize it directly in the class. 

@Hitesh Sharma  

Apex Basics → Variables/Conditions/Loops → List/Set/Map → sObjects → SOQL/SOSL → DML → Classes/Methods → Constructors → Triggers → Governor Limits & Bulkification → Test Classes → Async Apex → Integrations.

Practice every topic with small programs in Developer Console/VS Code.

Start with Salesforce's Apex Basics & Database module, then move to Apex Triggers and Apex Testing. Apex Basics & Database – Trailhead Apex Developer Guide 

Hi @Hitesh Sharma, 

You can use 

After authorizing the org, use SFDX: Retrieve Source from Org in VS Code to retrieve the required components. 

For JSON files, it depends on where they are stored: 

• Static Resource/LWC bundle → retrieve the corresponding metadata. 
• Salesforce record/data → use SOQL, Data Loader, or another data-export tool. 

Hope this helps! 

Hello @Hitesh Sharma

Lists, Sets, and Maps are fundamental Apex collection types in Salesforce, differing primarily in how they organize, store, and retrieve data. 

1. List (Ordered Shopping List) 

   What it is: A row of items kept in the exact order you put them in. You can have identical items twice. 

   Salesforce Use Case: Holding a batch of records straight out of a database query (like a list of 50 new Contacts) where sequence matters. 

2. Set (Unique ID Bag) 

   What it is: A bag that holds items, but no duplicates are allowed. If you drop the same item in twice, it only stays once. 

   Salesforce Use Case: Collecting unique Account IDs from incoming records so you can search the database safely without running duplicate queries. 

3. Map (Name-to-Phone Number Directory) 

   What it is: A pair system where a unique "Key" points to a specific "Value" (like a person's name linked to their phone number). 

   Salesforce Use Case: Matching a record ID (Key) directly to its parent Account or Contact record (Value) for instant lookup. 

Best Practices 

- No Queries in Loops: Never run database queries inside loops; fetch data into a List or Map first. 

- Use Sets for IDs: Put record IDs into a Set when filtering via WHERE Id IN :mySet to keep code clean and fast. 

- Pick the Right Tool: Use a List for order, a Set for uniqueness, and a Map when you need to find a record instantly by its ID

@Deepak Sharma

I would use an after-trigger for all four events because the Account tier depends on the current set of Opportunities. Insert and undelete can introduce a qualifying Opportunity, update can change Amount, Stage, or Account, and delete can remove the Opportunity that previously determined the tier.  

For update, I collect both the old and new Account IDs so that an Opportunity moving between Accounts recalculates both Accounts.  

The handler passes a Set of Account IDs to a service class, which performs bulk SOQL, calculates the highest applicable tier in memory, and performs a single bulk Account update. This avoids SOQL and DML inside loops and handles bulk transactions safely.