I don't know how you take data out of SQL server then index with ES but I'm assuming you index your data in JSON format with ES. If you did this, take a look at the JSON output, if you see fields with no value, or empty string, or "null" string then I suggest to modify that code that generates the JSON output to skip those fields when their values are null or if you use Gson library for example, initialize all fields with null, when Gson converts your objects to JSON, it will skip fields that are null, they won't show up in the JSON output.