NHibernate QueryOver和subquery的问题

本文关键字：问题 subquery QueryOver NHibernate | 更新日期: 2023-09-27 17:53:29

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; }
}

我想写一个查询，带来所有的提交，其最后一个笔记是由一些用户或用户列表(通过他们的名字识别)输入的。我将感谢您的帮助，使用NHibernate QueryOver API构建这个查询。我已经能够创建一个查询来带来所有最后的笔记，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?或者你有其他的解决方案吗?

NHibernate QueryOver和subquery的问题

我会尝试这样做与子查询(未测试虽然)

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: 
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)

希望这将帮助。子查询返回日期而不是id可能存在问题。我和LMK会看看的

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