title: How to delete column in next version of room database Android?
body: <p>How to delete a column in next version of room database android.DROp or delete not working.?</p>
  
  <pre><code>@Database(entities = {User.class, AdTime.class}, version = 1, exportSchema = false)
    public abstract class AppDataBase extends RoomDatabase {
  
    private static AppDataBase INSTANCE;
  
    public abstract UserDao userModel();
  
    public abstract AdDao adModel();
  
    public static AppDataBase getInMemoryDatabase(Context context) {
  
      if (INSTANCE == null) {
          INSTANCE = Room.databaseBuilder(context, AppDataBase.class, "adrider")
                  // To simplify the codelab, allow queries on the main thread.
                  // Don't do this on a real app! See PersistenceBasicSample for an example.
                  .allowMainThreadQueries()
                //  .addMigrations(MIGRATION_1_2)
                  //  .fallbackToDestructiveMigration()
                  .build();
        }
        return INSTANCE;
      }
  
    static final Migration MIGRATION_1_2=new Migration(1,2) {
        @Override
        public void migrate(@NonNull SupportSQLiteDatabase database) {
            database.execSQL("ALTER TABLE User "
                  + "DROP Download");
        }
    };
  
  }
  </code></pre>