How to check for empty or null properties when fetching in Android?

Android
1

I’m trying to fetch data from a table with a column property value as null or empty. But it doesn’t work. I have used below codes:

BackendlessDataQuery dataQuery = new BackendlessDataQuery();
dataQuery.setWhereClause("status = 1 AND parent = '" + null + "'");
Backendless.Data.of(Category.class).find(dataQuery, categoryLoadingCallback);

BackendlessDataQuery dataQuery = new BackendlessDataQuery();
dataQuery.setWhereClause("status = 1 AND parent = '" + "" + "'");
Backendless.Data.of(Category.class).find(dataQuery, categoryLoadingCallback);
2

If “parent” is a relation column, then the following should work:

status = 1 AND parent is null