SQLite database

database

        SQLite Light weight No configuration required localization

         To borrow Class,DBHelper Inherit SQLiteOpenHelper

         Implement two abstract methods onCreate() onUpgrade() Create a constructor with parameters

          In the constructor Create database

         stay onCreate() In the method , Create tables and insert data

Find the problem ：

When the mobile phone is running , What is used to identify software ？

Package name

To operate a database

1. Create database

2. Create tables in the newly created database

The process of executing query statements

1. //1. Get database objects 
   SQLiteDatabase db=dbHelper.getWritableDatabase();
   //2. perform   Put the result set in the vernier caliper 
   Cursor cursor = db.rawQuery(sql, null);
   //3. Take out the results 
   List<Userinfo> list=new ArrayList<>();
   while (cursor.moveToNext()){
       Userinfo userinfo=new Userinfo();
       userinfo.setId(cursor.getInt(0));
       userinfo.setUser(cursor.getString(1));
       userinfo.setPwd(cursor.getString(2));
       list.add(userinfo);
   }
   //4. Release resources 
   cursor.close();
   db.close();
   

perform increase 、 Delete 、 Changed process  

1. Get database objects

SQLiteDatabase db=dbHelper.getWritableDatabase();

1. Executive action

String sql="delete from userinfo where id=?";

db.execSQL(sql,new String[]{"1"});

1. Release resources

db.close();