3

我有以下模型：

public class User
{
    public virtual int Id { get; set; }
    public virtual string Username { get; set; }
    public virtual string Password { get; set; }
    public virtual string Email { get; set; }
    public IList<SubmissionNote> Notes { get;set; }
}

public class SubmissionNote
{
    public virtual Int64 Id { get; set; }
    public virtual string Text { get; set; }
    public virtual DateTime CreatedOn { get; set; }
    public virtual User Creator { get; set; }
    public virtual Submission BelongsTo { get; set; }
}

public class Submission
{
    public virtual Int64 Id { get; set; }
    public virtual DateTime HappenedOn { get; set; }
    public virtual int StatusCode { get; set; }
}

我想编写一个查询，将所有提交的最后一个注释由某个用户或用户列表（由他们的名字标识）输入。感谢您使用 NHibernate QueryOver API 构建此查询的帮助。我已经能够创建一个查询来带来所有最后的注释，如下所示：

SubmissionNote alias = null;
var lastNote = session.QueryOver<SubmissionNote>()
    .SelectList(list => list.
        SelectGroup(x => x.BelongsTo).WithAlias(() => alias.BelongsTo).
        SelectMax(x => x.CreatedOn).WithAlias(() => alias.CreatedOn).
        Select(x => x.Creator).WithAlias(() => alias.Creator).
        Select(x => x.Id).WithAlias(() => alias.Id).
        Select(x => x.Text).WithAlias(() => alias.Text))
    .TransformUsing(Transformers.AliasToBean<SubmissionNote>())
    .List();

我可以使用指定的查询作为子查询来产生所需的结果吗？还是您建议其他解决方案？

4

1 回答 1

3

我会用子查询尝试这样的事情（虽然没有测试过）

SubmissionNote subNoteAlias = null, subNoteAliasMax =null;
User userAlias = null;
String[] userNames = new[]{"John","Joe"};

var subquery =
    QueryOver.Of(() => subNoteAliasMax)
       .Where(subNote => subNote.BelongsTo.Id == subNoteAlias.BelongsTo.Id)
       .Select(Projections.Max<SubmissionNote>(subNote => subNote.CreatedOn));

var result = session
 .QueryOver<SubmissionNote>(() => subNoteAlias)
 .WithSubquery.WhereProperty(subNote=>subNote.CreatedOn).Eq(subquery)
 .JoinQueryOver(
      subNote=>subNote.Creator
      ,()=>userAlias
      ,JoinType.InnerJoin
      ,Restrictions.In(Projections.Property(() => userAlias.Username ), userNames))
  .List();

生成的 SQL 查询将（非常）大致如下所示：

SELECT SubmissionNote.*
  FROM SubmissionNote INNER JOIN User
  ON SubmissionNote.creatorId = User.userId
  AND User.userName in ('john','joe')
  WHERE SubmissionNote.CreatedOn = (SELECT MAX(CreatedOn) FROM SubmissionNote snAlias     
     WHERE snAlias.SubmissionId = SubmissionNote.SubmissionId)

希望这会有所帮助。子查询返回日期而不是 id 可能存在问题。LMK，我会看看。

于 2013-01-16T09:57:19.443 回答