在数据库中生成随机问题

Question

我在Sqlite数据库中有5个表： 1.maths 2.boilogy 3.chemestry 4.physics 5.GK.

在所有表格中10问题。最后我们在测试页面中生成随机问题 那么什么是Sq lite数据库中的查询

public ArrayList<ExamModel> getRandomQuestion() {

    ArrayList<ExamModel> list = new ArrayList<ExamModel>();
    ExamModel model = null;

    Cursor cursor = null;

    cursor=myDataBase.query(tbl_MST_CA+","+tbl_MST_Exam+","+tbl_MST_Geography, null, null, null, null, null, "RANDOM()","15");


    if (cursor != null && cursor.getCount() > 0) {
        cursor.moveToFirst();

        for (int i = 0; i < cursor.getCount(); i++) {
            model = new ExamModel();

            model.setId(cursor.getInt(cursor.getColumnIndex("Id")));
            model.setAns1(cursor.getString(cursor.getColumnIndex("Answer1")));
            model.setAns2(cursor.getString(cursor.getColumnIndex("Answer2")));
            model.setAns3(cursor.getString(cursor.getColumnIndex("Answer3")));
            model.setAns4(cursor.getString(cursor.getColumnIndex("Answer4")));
            model.setQuestion(cursor.getString(cursor
                    .getColumnIndex("Question")));
            model.setTrueAnswer(cursor.getString(cursor
                    .getColumnIndex("TrueAnswer")));
            model.setLevelId(cursor.getInt(cursor.getColumnIndex("LevelId")));
            model.setExamId(cursor.getInt(cursor
                    .getColumnIndex("ExamIdRef")));

            list.add(model);

            cursor.moveToNext();
        }
    }
    if (cursor != null)
        cursor.close();


    return list;
}