SQL Logic Error or Missing Database with group_concat()

Question

I'm trying to use group_concat to group some rows into one in Android, I get the cursor, but when I request it to move to first position, it crashes with error "SQL Logic Error or Missing Database. If I remove group_concat() it works perfectly...

String sql = "SELECT group_concat(column2, '-') FROM myTable GROUP BY column1";

mCursor = mDb.rawQuery(sql, null);

if (mCursor != null) {
   mCursor.moveToFirst();
}

Am I doing something wrong???