房间数据库无法 return group_concat 列

Question

我正在尝试在房间中创建一个 DatabaseView 以从多个表中获取所需的数据。这是我的数据库视图：

@DatabaseView("SELECT site.name AS address, group_site.name AS groupName, group_site.member_id AS memberId " +
        "FROM site, group_site " +
        "INNER JOIN groupsite_join_site " +
        "ON site.id = groupsite_join_site.site_id AND group_site.id = groupsite_join_site.group_site_id " +
        "UNION SELECT preloaded_site.name AS address, preloaded_group_site.name AS groupName, preloaded_group_site.memberId AS memberId " +
        "FROM preloaded_site, preloaded_group_site " +
        "INNER JOIN preloaded_groupsite_join_site ON preloaded_site.id = preloaded_groupsite_join_site.site_id AND preloaded_site.id = preloaded_groupsite_join_site.site_id"
)
public class SiteDetail {
    long memberId;
    String address;
    String groupName;
}

这是我的 DAO：

@Dao
public interface SiteDetailDao {

    @Query("SELECT address, group_concat(groupName, ', '), memberId FROM sitedetail WHERE memberId = :memberId OR memberId = -1 GROUP BY address LIMIT 10")
    LiveData<List<SiteDetail>> getSiteDetailForMember(long memberId);
}

视图已按预期创建，但是，对视图的查询 returns 所有 groupNames 都为空。我已经使用数据库浏览器检查了查询，其中运行对 sqlite 本身的查询。 DB Browser returns 预期数据。包含 10 条记录的列表，每条记录如下：

|id|  address  |           groupName            |
| 1|youtube.com|videos, entertainment, streaming|

为什么会这样？ group_contact房间有问题吗？这是 SiteDetailDao_Impl:

  @Override
  public LiveData<List<SiteDetail>> getSiteDetailForMember(final long memberId) {
    final String _sql = "SELECT address, group_concat(groupName, ', '), memberId FROM sitedetail WHERE memberId = ? OR memberId = -1 GROUP BY address LIMIT 10";
    final RoomSQLiteQuery _statement = RoomSQLiteQuery.acquire(_sql, 1);
    int _argIndex = 1;
    _statement.bindLong(_argIndex, memberId);
    return __db.getInvalidationTracker().createLiveData(new String[]{"sitedetail"}, false, new Callable<List<SiteDetail>>() {
      @Override
      public List<SiteDetail> call() throws Exception {
        final Cursor _cursor = DBUtil.query(__db, _statement, false);
        try {
          final int _cursorIndexOfAddress = CursorUtil.getColumnIndexOrThrow(_cursor, "address");
          final int _cursorIndexOfMemberId = CursorUtil.getColumnIndexOrThrow(_cursor, "memberId");
          final List<SiteDetail> _result = new ArrayList<SiteDetail>(_cursor.getCount());
          while(_cursor.moveToNext()) {
            final SiteDetail _item;
            _item = new SiteDetail();
            final String _tmpAddress;
            _tmpAddress = _cursor.getString(_cursorIndexOfAddress);
            _item.setAddress(_tmpAddress);
            final long _tmpMemberId;
            _tmpMemberId = _cursor.getLong(_cursorIndexOfMemberId);
            _item.setMemberId(_tmpMemberId);
            _result.add(_item);
          }
          return _result;
        } finally {
          _cursor.close();
        }
      }

      @Override
      protected void finalize() {
        _statement.release();
      }
    });
  }

Answer 1

SiteDetailDao_Impl 的发布表明未生成代码来获取结果列 group_concat(groupName, ', ') 的值。我猜这是因为它没有简单的名字。因此，正如@sergiytikonov 在他的评论中建议的那样，您需要为该列提供一个别名。类似于：

group_concat(groupName, ', ') AS concatName

要支持新别名，请创建另一个 class（随意命名）：

public class SiteInfo {
    long memberId;
    String address;
    String concatName;
}

并将您的查询更改为 return LiveData<List<SiteInfo>>:

@Query("SELECT address, group_concat(groupName, ', ') AS concatName, memberId FROM sitedetail'" +
    " WHERE memberId = :memberId OR memberId = -1 GROUP BY address LIMIT 10")
LiveData<List<SiteInfo>> getSiteDetailForMember(long memberId);

房间数据库无法 return group_concat 列

Room database fails to return group_concat column

android

sqlite

android-sqlite

android-room

database-view