I have a requirement while creating contact if it already exists then it will update the existing ones.
For example we have 2 contacts which are duplicate and while creating new contact it shows us that already two contacts are there with same data. In that case newer one updates it info into the existing ones. I am trying it with trigger on contact.

trigger ContactDuplicateTrigger on Contact (before insert) {
   //private final Contact contact;
    
    // Initialize a list to hold any duplicate records
    private List<sObject> duplicateRecords;
    
    // Define variable that’s true if there are duplicate records
    public boolean hasDuplicateResult{get;set;}
    
    Profile userProfile = [SELECT Id FROM Profile WHERE Name='Sales User'];
    if(userProfile.Id = UserInfo.getProfileId())
    return;

    Contact cont = new Contact( FirstName= 'Robin', LastName='Singh',Email='pintub.sfdc@gmail.com' );
    Database.SaveResult saveResult = Database.insert(cont, false);
    if (!saveResult.isSuccess()) {
    for (Database.Error error : saveResult.getErrors()) {
     if (error instanceof Database.DuplicateError) {
         Database.DuplicateError duplicateError = (Database.DuplicateError)error;
         Datacloud.DuplicateResult duplicateResult = duplicateError.getDuplicateResult();

         ApexPages.Message errorMessage = new ApexPages.Message(
                            ApexPages.Severity.ERROR, 'Duplicate Error: ' + 
                            duplicateResult.getErrorMessage());
         ApexPages.addMessage(errorMessage);

         this.duplicateRecords = new List<sObject>();

         Datacloud.MatchResult[] matchResults = duplicateResult.getMatchResults();

         Datacloud.MatchResult matchResult = matchResults[0];
         Datacloud.MatchRecord[] matchRecords = matchResult.getMatchRecords();
         this.hasDuplicateResult = !this.duplicateRecords.isEmpty();
     }
}
}
}