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Closed Won Makes a Customer — Apex trigger practice problem · ForceChallenges

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Closed Won Makes a Customer

MediumApex Triggeron Opportunity 25 ptsCreated Oct 2, 2026

When an Opportunity moves to StageName = 'Closed Won' (i.e. it was not Closed Won before the update), set its parent Account's Type to 'Customer'.

Requirements:

Only react to the transition into Closed Won — compare against Trigger.oldMap.
Skip opportunities without an Account.
Your trigger must be bulk-safe: at most 1 SOQL query and 1 DML statement per 200-record chunk, regardless of how many opportunities change.

Constraints

Use Trigger.oldMap.get(opp.Id) to read prior values.
Collect Account Ids in a Set, then do one db.update.

after updateTrigger.oldMapBulkification

CodeApex

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Close 60 deals

Seed data

Account× 30 rows

Name: Prospect {{i}}Type: Prospect

Opportunity× 90 rows

Name: Deal {{i}}AccountId: {{id:Account:i%30+1}}CloseDate: {{date:i}}StageName: Negotiation/Review

DML under test

updateOpportunityWHERE Name LIKE 'Deal 1%'

SET

IsWon: trueIsClosed: trueStageName: Closed Won

Expected

Accounts with a won deal become CustomersSELECT COUNT() FROM Account WHERE Type = 'Customer' = 11
Other accounts untouchedSELECT COUNT() FROM Account WHERE Type = 'Prospect' = 19
Bulk-safe SOQL