@Mihai_Cog 

You have to split your merge statement into 2 parts. (Update and Insert/Delete).

MERGE INTO test t USING src s ON s.Id = t.Id and s.date_field = t.date_field and s.fields <> t.fields WHEN MATCHED THEN UPDATE SET * 

MERGE INTO test t USING src s ON s.Id = t.Id and s.date_field = t.date_field WHEN NOT MATCHED THEN INSERT * WHEN NOT MATCHED BY SOURCE THEN DELETE

In the first statement, you have to include all the columns where you don't want the update to happen if it's of the same value and then perform update. The second statement will help you insert and delete the records.