最近用litepal操作資料很方便，記錄下表關聯
1. 一對一
song和introduction 即音樂和簡介 Song中持有introduction 的引用，introduction 持有Song的引用，就建立了一對一關係，
- 增 如下面程式碼所示
- 刪 刪除song一行，對應的introduction 自動刪除，反之亦然。
- 改 修改introduction 某行,對應的song自動被修改

Introduction introduction = new Introduction();
introduction.setTitle("這是song1111 介紹");
Song song1 = new
 
 Song();
song1.setTitle("song111");
song1.setIntroduction(introduction);
introduction.save();
song1.save();
Song songData = DataSupport.findLast(Song.class, true);
Introduction introductionData = DataSupport.findLast(Introduction.class, true);
Log.e(TAG, "onCreate:songData " + songData);
Log.e(TAG, "onCreate:introductionData "
 
 + introductionData);

1. 多對一
   歌曲和評論 多對一

歌曲持有評論的集合即可
- 增 見程式碼
- 刪 刪多的一方，一的一方自動修改
- 改 同上

    Song song1 = new Song();
        song1.setTitle("song111");
        Commment comment1 = new Commment();
        comment1.setTitle("111");
        Commment comment2 = new Commment();
        comment2.setTitle("222"
 
);
        song1.getCommentList().add(comment1);
        song1.getCommentList().add(comment2);
        comment1.save();
        song1.save();

1. 多對多

Song song1 = new Song();
        song1.setTitle("song111");
        song1.save();


        Song song2 = new Song();
        song2.setTitle("song222");
        song2.save();


        Category category1 = new Category();
        category1.setTitle("111");
        category1.getSongArrayList().add(song1);
        category1.getSongArrayList().add(song2);
        category1.save();

        Category category2 = new Category();
        category2.setTitle("222");
        category2.getSongArrayList().add(song1);
        category2.getSongArrayList().add(song2);
        category2.save();