升級我的SQLite數據庫

Question

我對SQLite還是很陌生。
如何升級數據庫？

我以前的數據庫版本中有7個問題。
今天，我添加了大約13個新的，總共20個。
我使用addQuestion方法添加了它們。
但是，它不起作用。

我一直在修補我的onUpgrade。
我做錯了。

public class QuizHelper extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "creativequestion";
    private static final String TABLE_QUEST = "quest";
    private static final String KEY_ID = "qid";
    private static final String KEY_QUEST = "question";

    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_QUEST + " TEXT)";
        db.execSQL( sql );
        addQuestion();


    }

    private void addQuestion() {

        QuestionFaci q1 = new QuestionFaci( "OTHER USES: Name other uses of a Hammer. \n\n Example: Stir a soup." );
        this.addQuestion(q1);
        QuestionFaci q2 = new QuestionFaci( "RHYMES: Words that rhymes with Rice. \n\n Example: Ice" );
        this.addQuestion(q2);
        QuestionFaci q3 = new QuestionFaci( "WITH: I can cook eggs with... \n\n Example: A Piece of Plywood" );
        this.addQuestion(q3);
        QuestionFaci q4 = new QuestionFaci( "WITHOUT: I can wash my clothes without... \n\n Example: My Aunt" );
        this.addQuestion(q4);
        QuestionFaci q5 = new QuestionFaci( "I WILL: If I was Bill Gates, I will... \n\n Example: Buy a spaceship" );
        this.addQuestion(q5);
        QuestionFaci q6 = new QuestionFaci( "CREATE A MOVIE TITLE: A NIGHT \n\n Example: To Remember" );
        this.addQuestion(q6);
        QuestionFaci q7 = new QuestionFaci( "OTHER NAMES: Other names of a cow \n\n Example: Milk giver" );
        this.addQuestion(q7);
        QuestionFaci q8 = new QuestionFaci( "OTHER USES: Name other uses of a Cowboy Boots. \n\n Example: Pound a nail." );
        this.addQuestion(q8);
        QuestionFaci q9 = new QuestionFaci( "RHYMES: Bake a. \n\n Example: Flake." );
        this.addQuestion(q9);
        QuestionFaci q10 = new QuestionFaci( "I WILL: I will drive a helicopter \n\n Example: with eyes closed" );
        this.addQuestion(q10);
        QuestionFaci q11 = new QuestionFaci( "CREATE A TITLE: The Greatest \n\n Example: Heist" );
        this.addQuestion(q11);
        QuestionFaci q12 = new QuestionFaci( "CHANGE AN INGREDIENT: --- Cookie \n\n Example: Orange Chip" );
        this.addQuestion(q12);
        QuestionFaci q13 = new QuestionFaci( "FINISH ME: Can you remember the times when.. \n\n Example: push me over a cliff" );
        this.addQuestion(q13);
        QuestionFaci q14 = new QuestionFaci( "OTHER NAMES: Ball bearings \n\n Example: Mommy's new bangles" );
        this.addQuestion(q14);
        QuestionFaci q15 = new QuestionFaci( "FINISH ME: The donut rolls \n\n Example: down the hill" );
        this.addQuestion(q15);
        QuestionFaci q16 = new QuestionFaci( "RHYMES: Flip the \n\n Example: clip" );
        this.addQuestion(q16);
        QuestionFaci q17 = new QuestionFaci( "OTHER NAMES: Police \n\n Example: civilian peacekeeper" );
        this.addQuestion(q17);
        QuestionFaci q18 = new QuestionFaci( "CREATE A TITLE: Go Go \n\n Example: Changin" );
        this.addQuestion(q18);
        QuestionFaci q19 = new QuestionFaci( "I WILL: I will distribute screwdrivers \n\n Example: to all drivers" );
        this.addQuestion(q19);
        QuestionFaci q20 = new QuestionFaci( "CREATE A DISH: Chicken --- Soup \n\n Example: Dumpling" );
        this.addQuestion(q20);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldV, int newV) {
        String upgradeQuery = "ALTER TABLE quest ADD COLUMN question TEXT";
        if(newV>oldV)
            db.execSQL( upgradeQuery );
        onCreate( db );


    }

    private void addQuestion(QuestionFaci quest) {
        ContentValues values = new ContentValues(  );
        values.put(KEY_QUEST, quest.getQUESTION());
        dbase.insert( TABLE_QUEST, null, values );
    }


    public List<QuestionFaci> getAllQuestions(){
        List<QuestionFaci> quesList = new ArrayList<QuestionFaci>(  );
        String selectQuery = "SELECT * FROM " + TABLE_QUEST;
        dbase = this.getReadableDatabase();
        Cursor cursor = dbase.rawQuery( selectQuery, null );
        if (cursor.moveToFirst()){
            do{
                QuestionFaci quest = new QuestionFaci(  );
                quest.setID( cursor.getInt( 0 ) );
                quest.setQUESTION( cursor.getString( 1 ) );

                quesList.add(quest);
                } while (cursor.moveToNext());
         }

        return quesList;

    }
}

Answer 1

您應該將DATABASE_VERSION變量增加到例如2。這將調用onUpgrade方法。

這不是最佳方法，但是如果當前數據庫的版本更高，則可以刪除表，然后調用onCreate() 。

  @Override
    public void onUpgrade(SQLiteDatabase db, int oldV, int newV) {
        String upgradeQuery = "DROP TABLE IF EXISTS quest";
        db.execSQL( upgradeQuery );
        onCreate( db );    
    }

Answer 2

如前所述，如果保存的數據很簡單，則可以擦除Db，然后重新創建它。 如果其中還有其他數據，可能是用戶結果，用戶進度或其他任何數據，則需要在onUpgrade中正確處理更新。

我通常要做的是擁有一個onUpgrade，它將從android資源中讀取遷移文件。 這些文件將具有數據庫模式更改（如有必要）以及在版本之間遷移數據庫所需的任何更新語句。 我寧願沒有下面的case語句，而是動態地尋找遷移，但是這是一個必不可少的弊端，允許我在必要時定制和調整每個遷移。

@Override
   public void onUpgrade(SQLiteDatabase db, ConnectionSource connectionSource, int oldVersion, int newVersion)
   {
      AppLog.i(TAG, "onUpgrade, oldVersion=["+oldVersion+"], newVersion=["+newVersion+"]");
      try 
      {
          // Simply loop round until newest version has been reached and add the appropriate migration
          while (++oldVersion <= newVersion) 
          {
              switch (oldVersion) 
              {
              // The version in the case statement is the new (target) version. So case 2: will be an upgrade from 2 to 3.  
                  case 2: {
                      UpgradeUtils.addUpgrade(oldVersion);
                      break;
                  }
                  case 3: {
                      UpgradeUtils.addUpgrade(oldVersion);

                      break;
                  }
                  case 7: {
                     UpgradeUtils.addUpgrade(oldVersion);
                  }

                  case 8: {
                     UpgradeUtils.addUpgrade(oldVersion);
                  }
              }
          }
          // Get all the available updates
          final List<String> availableUpdates = UpgradeUtils.availableUpdates(DatabaseHelper.context.getResources());
          AppLog.d(TAG, "Found a total of " + availableUpdates.size() +" update statements" );

          for (final String statement : availableUpdates) 
          {
              db.beginTransaction();
              try {
                  AppLog.d(TAG, "Executing statement: " + statement);
                  db.execSQL(statement);
                  db.setTransactionSuccessful();
              }
              finally {
                  db.endTransaction();
              }
          }
      }
      catch (Exception e)
      {
         Log.e(TAG,"Error executing sql while upgrading database", e);
      }

   }

UpgradeUtils.java

public class UpgradeUtils
{
   private static final String TAG = "UpgradeHelper"; 

   protected static final Set<Integer> mVersionSet;
   static 
   {
      mVersionSet = new LinkedHashSet<Integer>();
   }

   public static final void addUpgrade(final int version) 
   {
      AppLog.d(TAG, "Adding " + version + " to upgrade path");
      mVersionSet.add(version);
  }

   public static List<String> availableUpdates(final Resources resources) 
   {
      final List<String> updates = new ArrayList<String>();

      for (Integer version : mVersionSet) 
      {
              // Migration files are kept in assets/updates/migration-X.sql
          String fileName = String.format("updates/migration-%s.sql", version);

          AppLog.d(TAG, "Adding db version [" + version + "] to update list, loading file ["+ fileName +"]" );

          final String sqlStatements = DBUtils.loadAssetFile(resources, fileName);

          final String[] splitSql = sqlStatements.split("\\r?\\n");
          for (final String sql : splitSql) 
          {
              if (DBUtils.isNotComment(sql)) 
              {
                  updates.add(sql);
              }
          }
      }
      return updates;
  }

您還應該考慮從資源文件加載問題。