Как выбрать определенный диапазон строк (например, от 20 до 30) из базы данных Sqlite, а затем рандомизировать их

Question

Предположим, у вас есть база данных из 40 вопросов

Теперь можно выбрать вопросы с 1 по 10 по порядку, а затем выбрать случайные вопросы ч / б

например, у меня 40 вопросовон выбирает вопросы с 1 по 10, вопросы выше 10 не выбираются, а затем задают вопросы с 1 по 10 в случайном порядке

    public class QuizHelper extends SQLiteOpenHelper {
    private static final int DATABASE_VERSION = 1;
    // Database Name
    private static final String DATABASE_NAME = "mathsone";
    // tasks table name
    private static final String TABLE_QUEST = "quest";
    // tasks Table Columns names
    private static final String KEY_ID = "qid";
    private static final String KEY_QUES = "question";
    private static final String KEY_ANSWER = "answer"; // correct option
    private static final String KEY_OPTA = "opta"; // option a
    private static final String KEY_OPTB = "optb"; // option b
    private static final String KEY_OPTC = "optc"; // option c
    private SQLiteDatabase dbase;
    public QuizHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        dbase = db;
        String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_QUEST + " ( "
                + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_QUES
                + " TEXT, " + KEY_ANSWER + " TEXT, " + KEY_OPTA + " TEXT, "
                + KEY_OPTB + " TEXT, " + KEY_OPTC + " TEXT)";
        db.execSQL(sql);
        addQuestion();

    }
    private void addQuestion() {
        Question q1 = new Question("5+2 = ?", "7", "8", "6", "7");
        this.addQuestion(q1);
        Question q2 = new Question("2+18 = ?", "18", "19", "20", "20");
        this.addQuestion(q2);
        Question q3 = new Question("10-3 = ?", "6", "7", "8", "7");
        this.addQuestion(q3);
        Question q4 = new Question("5+7 = ?", "12", "13", "14", "12");
        this.addQuestion(q4);
        Question q5 = new Question("3-1 = ?", "1", "3", "2", "2");
        this.addQuestion(q5);
        Question q6 = new Question("0+1 = ?", "1", "0", "10", "1");
        this.addQuestion(q6);
        Question q7 = new Question("9-9 = ?", "0", "9", "1", "0");
        this.addQuestion(q7);
        Question q8 = new Question("3+6 = ?", "8", "7", "9", "9");
        this.addQuestion(q8);
        Question q9 = new Question("1+5 = ?", "6", "7", "5", "6");
        this.addQuestion(q9);
        Question q10 = new Question("7-5 = ?", "3", "2", "6", "2");
        this.addQuestion(q10);
        Question q11 = new Question("7-2 = ?", "7", "6", "5", "5");
        this.addQuestion(q11);
        Question q12 = new Question("3+5 = ?", "8", "7", "5", "8");
        this.addQuestion(q12);
        Question q13 = new Question("0+6 = ?", "7", "6", "5", "6");
        this.addQuestion(q13);
        Question q14 = new Question("12-10 = ?", "1", "2", "3", "2");
        this.addQuestion(q14);
        Question q15 = new Question("12+2 = ?", "14", "15", "16", "14");
        this.addQuestion(q15);
        Question q16 = new Question("2-1 = ?", "2", "1", "0", "1");
        this.addQuestion(q16);
        Question q17 = new Question("6-6 = ?", "6", "12", "0", "0");
        this.addQuestion(q17);
        Question q18 = new Question("5-1 = ?", "4", "3", "2", "4");
        this.addQuestion(q18);
        Question q19 = new Question("4+2 = ?", "6", "7", "5", "6");
        this.addQuestion(q19);
        Question q20 = new Question("5+1 = ?", "6", "7", "5", "6");
        this.addQuestion(q20);
        Question q21 = new Question("5-4 = ?", "5", "4", "1", "1");
        this.addQuestion(q21);

    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldV, int newV) {

        db.execSQL("DROP TABLE IF EXISTS " + TABLE_QUEST);

        onCreate(db);
    }
    // Adding new question
    public void addQuestion(Question quest) {
        ContentValues values = new ContentValues();
        values.put(KEY_QUES, quest.getQUESTION());
        values.put(KEY_ANSWER, quest.getANSWER());
        values.put(KEY_OPTA, quest.getOPTA());
        values.put(KEY_OPTB, quest.getOPTB());
        values.put(KEY_OPTC, quest.getOPTC());
        dbase.insert(TABLE_QUEST, null, values);
    }
    public List<Question> getAllQuestions() {
        List<Question> quesList = new ArrayList<Question>();
        String selectQuery = "SELECT * FROM " + TABLE_QUEST;
        dbase = this.getReadableDatabase();
        Cursor cursor = dbase.rawQuery(selectQuery, null);
        if (cursor.moveToFirst()) {
            do {
                Question quest = new Question();
                quest.setID(cursor.getInt(0));
                quest.setQUESTION(cursor.getString(1));
                quest.setANSWER(cursor.getString(2));
                quest.setOPTA(cursor.getString(3));
                quest.setOPTB(cursor.getString(4));
                quest.setOPTC(cursor.getString(5));
                quesList.add(quest);
            } while (cursor.moveToNext());
        }

        return quesList;
    }
}

я пытался сделать

String selectQuery = "SELECT * FROM " + TABLE_QUEST + " ORDER BY RANDOM() LIMIT 10";

, но это ограничивает только числовопрос, который требуется, я хочу, например, взять вопрос от 20 до 30, и только те вопросы, а не другие из базы данных, и задать вопрос между ними в случайном порядке

Answer 1

Вам просто нужно добавить предложение WHERE , чтобы ограничить выбранные строки, например: -

SELECT * FROM quest WHERE qid >= 20 and qid <= 30  ORDER BY RANDOM() LIMIT 10;

Примите во внимание следующее: -

DROP TABLE IF EXISTS quest;
CREATE TABLE IF NOT EXISTS quest (qid INTEGER PRIMARY KEY, question TEXT, answer TEXT, opta TEXT, optb TEXT, optc TEXT);
INSERT INTO quest (question,answer,opta,optb,optc) VALUES 
    ("5+2 = ?", "7", "8", "6", "7"),
    ("2+18 = ?", "18", "19", "20", "20"),
    ("10-3 = ?", "6", "7", "8", "7"),
    ("5+7 = ?", "12", "13", "14", "12"),
    ("3-1 = ?", "1", "3", "2", "2"),
    ("0+1 = ?", "1", "0", "10", "1"),
    ("9-9 = ?", "0", "9", "1", "0"),
    ("3+6 = ?", "8", "7", "9", "9"),
    ("1+5 = ?", "6", "7", "5", "6"),
    ("7-5 = ?", "3", "2", "6", "2"),
    ("7-2 = ?", "7", "6", "5", "5"),
    ("3+5 = ?", "8", "7", "5", "8"),
    ("0+6 = ?", "7", "6", "5", "6"),
    ("12-10 = ?", "1", "2", "3", "2"),
    ("12+2 = ?", "14", "15", "16", "14"),
    ("2-1 = ?", "2", "1", "0", "1"),
    ("6-6 = ?", "6", "12", "0", "0"),
    ("5-1 = ?", "4", "3", "2", "4"),
    ("4+2 = ?", "6", "7", "5", "6"),
    ("5+1 = ?", "6", "7", "5", "6"),
    ("5-4 = ?", "5", "4", "1", "1"),
    ("5+2 = ?", "7", "8", "6", "7"),
    ("2+18 = ?", "18", "19", "20", "20"),
    ("10-3 = ?", "6", "7", "8", "7"),
    ("5+7 = ?", "12", "13", "14", "12"),
    ("3-1 = ?", "1", "3", "2", "2"),
    ("0+1 = ?", "1", "0", "10", "1"),
    ("9-9 = ?", "0", "9", "1", "0"),
    ("3+6 = ?", "8", "7", "9", "9"),
    ("1+5 = ?", "6", "7", "5", "6"),
    ("7-5 = ?", "3", "2", "6", "2"),
    ("7-2 = ?", "7", "6", "5", "5"),
    ("3+5 = ?", "8", "7", "5", "8"),
    ("0+6 = ?", "7", "6", "5", "6"),
    ("12-10 = ?", "1", "2", "3", "2"),
    ("12+2 = ?", "14", "15", "16", "14"),
    ("2-1 = ?", "2", "1", "0", "1"),
    ("6-6 = ?", "6", "12", "0", "0"),
    ("5-1 = ?", "4", "3", "2", "4"),
    ("4+2 = ?", "6", "7", "5", "6"),
    ("5+1 = ?", "6", "7", "5", "6"),
    ("5-4 = ?", "5", "4", "1", "1")
;
SELECT * FROM quest WHERE qid >= 20 and qid <= 30  ORDER BY RANDOM() LIMIT 10;

• Обратите внимание на 42 вопроса, но для удобства некоторые вопросы повторяются.Однако столбец qid является уникальным для строки, которая используется в качестве индикатора выбранной строки.
• Поскольку диапазон составляет 20-30 (11 строк), а LIMIT равен 10тогда 1 строка всегда будет опущена.

Результат может быть: -

Результат может быть: -

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