Selecting NULL values in Android SQLite
android, sqlite
Solution
Android's database API does not allow to pass `NULL` values as parameters; it allows only strings. (This is a horrible design bug. Even worse, SQLiteStatement does allow all types for parameters, but works only for queries that return a single value.)
You have no choice but to change the query string to `blah IS NULL`.
Problem
I'm executing the following method with no success beacause of the selectArgs being incorrect (at least this is what I believe. findAll: ``` public Collection<Object> findAllByCodigoSetorOrderByStatusWhereDataAgendamentoIsNull(Integer vendedor) { Collection<Object> objects = null; String selection = Object.FIELDS[20] + "=?" + " OR " + Object.FIELDS[20] + "=?" + " OR " + Object.FIELDS[20] + "=?" + " AND " + Object.FIELDS[6] + "=?"; String[] selectionArgs = new String[] { "''", "'null'", "NULL", String.valueOf(vendedor) }; Collection<ContentValues> results = findAllObjects(Object.TABLE_NAME, selection, selectionArgs, Object.FIELDS, null, null, Object.FIELDS[4]); objects = new ArrayList<Object>(); for (ContentValues result : results) { objects.add(new Object(result)); } return objects; } ``` findAllObjects: ``` protected Collection<ContentValues> findAllObjects(String table, String selection, String[] selectionArgs, String[] columns, String groupBy, String having, String orderBy) { Cursor cursor = null; ContentValues contentValue = null; Collection<ContentValues> contentValues = null; try { db = openRead(this.helper); if (db != null) { cursor = db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy); contentValues = new ArrayList<ContentValues>(); for (int i = 0; i < cursor.getCount(); i++) { cursor.moveToPosition(i); contentValue = new ContentValues(); for (int c = 0; c < cursor.getColumnCount(); c++) { contentValue.put(cursor.getColumnName(c), cursor.getString(c)); } contentValues.add(contentValue); cursor.moveToNext(); } } return contentValues; } finally { close(db); } } ``` How can I correctly select and compare a column to - null, 'null' and '' using the db.query?