Querying Opportunity Field History for a custop lookup fields gives 2 record back for a single change in the field

Question

I am trying to query Opportunity Field History to get the results for a custom lookup field that has history tracking. I am getting 2 records back for 1 single change, one of the record has oldvalue and newvalue as lookup id and another record has lookup name as old and new value. I was wondering why Field history is creating 2 records for same change. I am trying to query it and set the resulting list to a front end table, but since it is returning 2 values for single change there is a duplicate value displayed. how can i restrict that?

my query looks like this select id, OldVlaue, NewVlaue from OpportunityFieldHistory where OpportunityId='oppID'

Answer 1

This is "working-as-designed"

For example, field history on Opportunity.OwnerId will return two records

OldValue      NewValue
----------     --------
oldId          newId
oldOwner.Name  newOwner.Name  // facilitates display in the Related List

Since you can't filter on OldValue or NewValue in the query; you'll need to post-process in Apex, testing OldValue / NewValue to see if they cast to ID type

try {
   Id oldValAsId = (Id) fieldHistoryItem.OldValue;
}
 catch (Exception e) { // ignore item  }