Android SQLite數據庫選擇隨機查詢

Question

我想用此代碼選擇隨機行，但我不能，每當我修改代碼時，它總是顯示數據庫中添加的第一個問題。我必須做我的表中選擇隨機行

public int rowcount() 
{ 
    int row=0; 
    String selectQuery = "SELECT * FROM " + TABLE_QUEST; 
    SQLiteDatabase db = this.getWritableDatabase(); 
    Cursor cursor = db.rawQuery(selectQuery, null); 
    row=cursor.getCount(); 
    return row; 
} 

---

這裏是整個代碼DbHelper.java

import java.util.ArrayList; 
import java.util.List; 
import android.content.ContentValues; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 
public class DbHelper extends SQLiteOpenHelper { 
    private static final int DATABASE_VERSION = 1; 
    // Database Name 
    private static final String DATABASE_NAME = "triviaQuiz"; 
    // tasks table name 
    private static final String TABLE_QUEST = "quest"; 
    // tasks Table Columns names 
    private static final String KEY_ID = "id"; 
    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 DbHelper(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);   
     addQuestions(); 
     //db.close(); 
    } 
    private void addQuestions() 
    { 
     Question q1=new Question("Which company is the largest manufacturer" + 
       " of network equipment?","HP", "IBM", "CISCO", "CISCO"); 
     this.addQuestion(q1); 
     Question q2=new Question("Which of the following is NOT " + 
       "an operating system?", "SuSe", "BIOS", "DOS", "BIOS"); 
     this.addQuestion(q2); 
     Question q3=new Question("Which of the following is the fastest" + 
       " writable memory?","RAM", "FLASH","Register","Register"); 
     this.addQuestion(q3); 
     Question q4=new Question("Which of the following device" + 
       " regulates internet traffic?", "Router", "Bridge", "Hub","Router"); 
     this.addQuestion(q4); 
     Question q5=new Question("Which of the following is NOT an" + 
       " interpreted language?","Ruby","Python","BASIC","BASIC"); 
     this.addQuestion(q5); 
    } 
    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldV, int newV) { 
     // Drop older table if existed 
     db.execSQL("DROP TABLE IF EXISTS " + TABLE_QUEST); 
     // Create tables again 
     onCreate(db); 
    } 
    // Adding new question 
    public void addQuestion(Question quest) { 
     //SQLiteDatabase db = this.getWritableDatabase(); 
     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()); 
     // Inserting Row 
     dbase.insert(TABLE_QUEST, null, values);   
    } 
    public List<Question> getAllQuestions() { 
     List<Question> quesList = new ArrayList<Question>(); 
     // Select All Query 
     String selectQuery = "SELECT * FROM " + TABLE_QUEST; 
     dbase=this.getReadableDatabase(); 
     Cursor cursor = dbase.rawQuery(selectQuery, null); 
     // looping through all rows and adding to list 
     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 quest list 
     return quesList; 
    } 
    public int rowcount() 
    { 
     int row=0; 
     String selectQuery = "SELECT * FROM " + TABLE_QUEST; 
     SQLiteDatabase db = this.getWritableDatabase(); 
     Cursor cursor = db.rawQuery(selectQuery, null); 
     row=cursor.getCount(); 
     return row; 
    } 
} 

Answer 1

的COUNT（*）費了很多，但如果你能緩存它，那麼差異不應該那麼大，當你有很多行時，它本身比「隨機排序（）」要快得多，儘管它們有一些不方便。 （即少數缺失）

如果你行的IDS是相當包裝，那麼你就可以做到以下幾點：

select * from foo where rowid = (abs(random()) % (select max(rowid)+1 from foo));