public class MyDatabaseHelper extends SQLiteOpenHelper {//把数据库建表指令弄成一个字符串CREATE_BOOK常量public static final String CREATE_BOOK = "create table book ("+ "id integer primary key autoincrement, "+ "author text, "+ "price real, "+ "pages integer, "+ "name text)";public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {super(context,name,factory,version);}@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL(CREATE_BOOK);//执行建表Log.d(TAG,"数据库初始化完成");}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}}

    private MyDatabaseHelper dbHelper = new MyDatabaseHelper(this, "BookStore.db", null, 1);//新建一个MyDatabaseHelper对象，上下文；数据库名；第三个参数允许我们在查询数据的时候返回一个自定义的 Cursor，一般都是传入 null；数据库版本号dbHelper.getWritableDatabase();

    public class MyDatabaseHelper extends SQLiteOpenHelper {//把数据库建表指令弄成一个字符串CREATE_BOOK常量public static final String CREATE_BOOK = "create table book ("+ "id integer primary key autoincrement, "+ "author text, "+ "price real, "+ "pages integer, "+ "name text)";//integer 表示整型，real 表示浮点型，text 表示文本类型，blob 表示二进制类型。另外，上述建表语句中我们还//使用了 primary key 将 id 列设为主键，并用 autoincrement 关键字表示 id 列是自增长的public static final String CREATE_CATEGORY = "create table category("+ "id integer primary key autoincrement, "+ "category_name text, "+ "category_code integer)";public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {super(context,name,factory,version);}@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL(CREATE_BOOK);//执行建表
            db.execSQL(CREATE_CATEGORY);Log.d(TAG,"数据库初始化完成");}//当检测到数据库版本变化，就会执行onUpgrade()中的代码
        @Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {//调用SQL语句，若存在表格则删去，之后在重新调用onCreate()方法db.execSQL("drop table if exists Book");db.execSQL("drop table if exists Category");onCreate(db);}}

    @Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {//调用SQL语句，若存在表格则删去，之后在重新调用onCreate()方法/*** 注释时间：20170117* 代码作用：覆盖式更新数据库，删除之前的数据库再新建库* 注释原因：学习新的数据库更新方法db.execSQL("drop table if exists Book");db.execSQL("drop table if exists Category");onCreate(db);*/switch (newVersion){case 2:db.execSQL(CREATE_CATEGORY);//！！！注意，无break；case 3:db.execSQL("alter table Book add column category_id integer");//！！！注意，无break；//因为无论覆盖哪一个版本安装，都需要安装其他更新，从第二版安装第三版时，只需要更新case3,确保数据库最新Log.d(TAG,"第3版数据库更新成功");break;default:Log.d(TAG,"数据库更新失败");break;}}

SQLiteDatabase db = dbBookStoreHelper.getWritableDatabase();//新建两个数据db.execSQL("insert into Book (name, author, pages, price) values(?, ?, ?, ?)",new String[] { "The Da Vinci Code", "Dan Brown", "454", "16.96" });db.execSQL("insert into Book (name, author, pages, price) values(?, ?, ?, ?)",new String[] { "The Lost Symbol", "Dan Brown", "510", "19.95" });//查询所有数据db.rawQuery("select * from Book", null);//把《The Da Vinci Code》这本书改成10.99db.execSQL("update Book set price = ? where name = ?", new String[] { "10.99","The Da Vinci Code" });//把500页以上的书删了db.execSQL("delete from Book where pages > ?", new String[] { "500" });

//！！！先组装数据，再插入数据
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
// 开始组装第一条数据
values.put("name", "The Da Vinci Code");
values.put("author", "Dan Brown");
values.put("pages", 454);
values.put("price", 16.96);
db.insert("Book", null, values); // 插入第一条数据
values.clear();
// 开始组装第二条数据
values.put("name", "The Lost Symbol");
values.put("author", "Dan Brown");
values.put("pages", 510);
values.put("price", 19.95);
db.insert("Book", null, values); // 插入第二条数据

SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("price", 10.99);
db.update("Book", values, "name = ?", new String[] { "The DaVinci Code" });
values.clean();

db.delete("Book","pages > ?",new String[] {"300"});

Cursor cursor = db.query("Book",null,"1",null,null,null,null);if (cursor != null){if(cursor.moveToFirst()){do {//直到型循环String name = cursor.getString(cursor.getColumnIndex("name"));String author = cursor.getString(cursor.getColumnIndex("author"));Double price = cursor.getDouble(cursor.getColumnIndex("price"));int pages = cursor.getInt(cursor.getColumnIndex("pages"));Log.d(TAG,"name = " + name);Log.d(TAG,"author = " + author);Log.d(TAG,"price = " + price);Log.d(TAG,"pages = " + pages);}while (cursor.moveToNext());}}cursor.close();

    db.beginTransaction();//开始事务try {db.delete("Book", null, null);if (true) {// 在这里手动抛出一个异常，让事务失败throw new NullPointerException();}db.execSQL("insert into Book (name, author, pages, price) values(?, ?, ?, ?)",new String[]{"马克思主义2", "中国**党", "1000", "100.00"});//居然和谐db.setTransactionSuccessful(); // 事务已经执行成功} catch (Exception e) {e.printStackTrace();} finally {db.endTransaction(); // 结束事务}