Need help with writing a trigger on Opportunity object to update Lookup field at opportunity level based on the look field value in account object

Question

I initially wrote the below trigger to update opportunity field based on value in account field. However, it should be other way around.

Explaining: When an opportunity is created/Edited and if the lookup field at account level called Sales_Manager__c in not null, the same value should be populated onto Opportunity lookup field Sales_Manager__c

trigger updateOppSalesManager on Account (After update)  
    {
    /* checking the value of sales manager at account level by looping through Opportunities */ 
      List<Opportunity> opps = [
            Select Id, sales_manager__c, account.sales_manager__c
            From Opportunity
            Where AccountId In :Trigger.newMap.keySet()
        ];

        /* Updating opportunity field with the value from account Sales_manager__c*/
        for (Opportunity opp : opps) {
            opp.sales_manager__c = opp.Account.sales_manager__c;
        }
        update opps;

}

I tried in every possible way i can by using set: to set account id , list: to loop through opportunity with the account ID , also used maps, but with no luck. Any Help, Suggestion, Guidence will be very useful for me.

Thank you Sam

Answer 1

You could try something like this. Please forgive any typos.

trigger updateOppSalesManager on Account (After update)  
    {
    //Create Sets and Lists
    Set<ID> OppAcc = New Set<id>();
    List<Opportunity> opps = New List<Opportunity>();

    //Loop through inbound opps and add the accountid to the ID set
    For(Opportunity o : Trigger.New)
    {
        OppAcc.add(o.Accountid);
    }    

    Map<id, account> AccMap=new Map<id, account>();
    AccMap.putAll([select id, Sales_Manager__c from Account where id in :OppAcc]);    

    //Loop back through the same opps. Link the account through the map above, then match the 2 fields. Finally, add the opp to a list for bulk updates.
    For(Opportunity o : Trigger.New)
    {
        Account a = AccMap.get(o.Account);
        o.sales_manager__c = a.sales_manager__c;
        opps.add(o);
    }    

    //make sure that you are only running an update if anything is in the list to update. Otherwise, you will get an error message.
    if(opps.size() > 0)
    {
        update opps;
    }

}

Answer 2

You can accomplish this in the process builder on the Opportunity object.

Steps:

1. Select the Opportunity Object and start when created or edited
2. Set Criteria to look at the related Account Sales Manager and see if it is not null and if it does not match what is already on oppty record.
3. Update Sales Manager on Opportunity with a Reference to the related Account Sales Manager.

Answer 3

Add a formula field on Opportunity that displays the Sales_Manager__c custom field on the account object.