Need Help on Writing trigger on Junction Object

Question

I have a Junction object called "LOCATION JUNCTION", and it has two master-detail relationships to Opportunity and Location

When I create new junction object records like

1. name1 opp1 loca1 
2. name2 opp2 loca1 

The system should throw an error like

"please select different location"

(FOR one account if  opp1 is having location1 then opp2 should not take location1) (Opportunities under same account should not have same location) How should I write a trigger on this junction object. Please suggest.

Thanks

Answer 1

I am assuming junction object name is LocationJunction__c and location field name is Location__c.

Following code will only process one record properly. Click to Bulkify your trigger

trigger LocationJunctionTrigger on LocationJunction__c (after insert,after Update)
{
    if(trigger.isAfter && (trigger.isInsert || trigger.isUpdate))
    {
        List<LocationJunction__c> currentList = [SELECT Id,Location__c,Opportunity__r.AccountId from LocationJunction__c WHERE Location__c=:trigger.new[0].Location__c AND Id IN : trigger.new];
        List<LocationJunction__c> existingList = [SELECT Id,Location__c,Opportunity__r.AccountId from LocationJunction__c WHERE Location__c=:trigger.new[0].Location__c AND Id Not IN : trigger.new];

        for(LocationJunction__c currentLocation : currentList)
        {
            for(LocationJunction__c existingLocation : existingList)
                if(existingLocation.Opportunity__r.AccountId == currentLocation.Opportunity__r.AccountId)
                    trigger.new[0].adderror('Please select different location');
        }
    }
}

Answer 2

You can try below code

trigger LocationJunctionCRUD on LocationJunction__c (before insert) 
{

 List<Id> lstOpportunity= new List<Id>();

  Map<Id,Id> mapOppLoc= new Map<Id,Id>();
    for(LocationJunction__c  locationJunction: Trigger.new){
        lstOpportunity.add(locationJunction.Opportunity__c);
        mapOppLoc.put(locationJunction.Opportunity__c,locationJunction.Location__c );
    }


if(lstOpportunity != null && lstOpportunity.size()>0){

   List<LocationJunction__c> lstlocationJunction= [Select id,Opportunity__c,Location__c from LocationJunction__c
                                     where Opportunity__c in :lstOpportunity];

 if(lstlocationJunction!= null && lstlocationJunction.size()>0){    
    for(LocationJunction__c locationJunction:lstlocationJunction){

 if(locationJunction.Location__c == mapOppCamp.get(locationJunction.Opportunity__c))
{
              trigger.new[0].adderror('This Location already exist in other record');

  }

}

 }                         

 } 

}

Hope this helps.