我正在尝试从我的数据库中删除一个表,所以我按照官方说明进行操作。这就是我的代码的样子:
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// A list of the values I want to preserve
String contents = Values.KEY_ROWID + ","
+ Values.KEY_NAME + ","
+ Values.COURSE_KEY_TEACHER + ","
+ Values.KEY_DESCRIPTION + ","
+ Values.KEY_ROOM + ","
+ Values.COURSE_KEY_TIMES_OF_DAY + ","
+ Values.COURSE_KEY_COLOR;
db.execSQL("CREATE TABLE course_backup("
+ Values.KEY_ROWID + " int, "
+ Values.KEY_NAME + " text not null, "
+ Values.COURSE_KEY_TEACHER + " text not null, "
+ Values.KEY_DESCRIPTION + " text, "
+ Values.KEY_ROOM + " int, "
+ Values.COURSE_KEY_TIMES_OF_DAY + " text, "
+ Values.COURSE_KEY_COLOR + " int not null);");
db.execSQL("INSERT INTO course_backup SELECT "
+ contents
+ " FROM course_backup;");
/*db.execSQL("DROP TABLE " + Values.COURSE_TABLE + ";");
db.execSQL(Values.COURSE_DATABASE_CREATE);
db.execSQL("INSERT INTO " + Values.COURSE_TABLE + " SELECT "
+ contents + " FROM course_backup");*/
}
但是当我将数据库的副本拉到我的计算机上并查看 course_backup 表时,它完全是空的。所有列都是正确创建的,但没有一行数据。我究竟做错了什么?