Question

我有数据库comments.db我已经创建了一个表table_comments 我想在这个数据库中创建第二个表（table_birthday）。我的问题是如何在现有数据库中添加此表？我有以下代码。任何帮助表示赞赏。

package com.example.proj1;


import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class MySQLiteHelper extends SQLiteOpenHelper {

    //table 1
    public static final String TABLE_COMMENTS = "comments";
      public static final String COLUMN_ID = "_id";
      public static final String COLUMN_COMMENT = "comment";

      //table 2
      public static final String TABLE_BIRTHDAY = "birthday";
      public static final String Birthday_ID = "_id";
      public static final String COLUMN_Birthday = "bday";

      //database
      private static final String DATABASE_NAME = "commments.db";
      private static final int DATABASE_VERSION = 1;

      // table 1
      private static final String DATABASE_CREATE = "create table "
          + TABLE_COMMENTS + "(" + COLUMN_ID
          + " integer primary key autoincrement, " + COLUMN_COMMENT
          + " text not null);";

      //table 2
      private static final String DATABASE_CREAT = "create table "
              + TABLE_BIRTHDAY + "(" + Birthday_ID
              + " integer primary key autoincrement, " + COLUMN_Birthday
              + " text not null);";


      public MySQLiteHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
          }


    @Override
    public void onCreate(SQLiteDatabase database) {
        database.execSQL(DATABASE_CREATE);
        database.execSQL(DATABASE_CREAT);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.w(MySQLiteHelper.class.getName(),"Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXISTS " + TABLE_COMMENTS);
            db.execSQL("DROP TABLE IF EXISTS " + TABLE_BIRTHDAY);
            onCreate(db);

    }

}

Answer 1

使用应用管理器擦除您的应用数据，或者只是卸载并重新安装您的应用。

您的测试环境已经有一个架构版本为1的数据库，当您通过添加另一个表来修改架构时，由于架构版本相同且数据库已存在，因此不会升级或创建数据库。

对于已发布的版本，您应该提升DB_VERSION并在onUpgrade()中实施相应的迁移代码。

如何在sqlite数据库中添加第二个表

1 个答案: