Unique values from one column using ActiveAndroid? - activeandroid

Question

I'm trying to get all unique values from a single column from a table. I'm utterly failing, and the docs don't seem to go into enough depth, and what I've gleaned from looking at the source seems like that should help, but doesn't.
List<Question> questions = new Select().from(Question.class).where("ZCLASSLEVEL = ? ", classLevel).execute();
works to get all the columns of all the Questions.
However,
List<Question> questions = new Select(columns).from(Question.class).where("ZCLASSLEVEL = ? ", classLevel).execute();
doesn't return any data (questions.size() = 0), where I've tried
String[] columns = { "ZHRSSECTION" };
and
Select.Column[] columns = { new Select.Column("ZHRSSECTION", "ZHRSSECTION")};
Presumably, throwing .distinct(). after the Select() should return only unique values, but I can't even get just the single column I'm interested in to get returned.
What am I missing here?
Thanks!
randy

Answer 1

You should use groupBy() method to make the use of distinct() method.
For example:
List<Question> questions = new Select()
.distinct()
.from(Question.class)
.groupBy("ZCLASSLEVEL")
.execute();
The above code returns a list of Questions, one for each ZCLASSLEVEL (probably the last row).
Then you can get the unique values of ZCLASSLEVEL as
for(Question question: questions){
int level = question.ZCLASSLEVEL;
//do something with level.
}

Answer 2

A little late in answering this, but the issue is because SQLiteUtils.rawQuery() makes the assumption that the Id column is always going to be in the cursor result. Set your columns String[] to {Id, ZHRSSECTION} and you'll be fine.
List<FooRecord> list = new Select(new String[]{"Id,tagName"}).from(FooRecord.class).execute();