[英]Setting value based on different table in NHibernate query
I am using NHibernate, and have problems with this query... I have a class Item which I want to fetch using its Id. 我正在使用NHibernate,并且对此查询有问题...我有一个类项目,我想使用其Id获取。 All fine. 一切都很好。 However, I also want a bool property on the Item class to be set to true if some other condition is set. 但是,如果设置了其他条件,我还希望将Item类中的bool属性设置为true。 Specifically this property is named IsMarked, telling if the Item is marked/stared/flagged for the user that requested it, and this information is set on a table giving the relation between Item and User. 具体来说,此属性名为IsMarked,告知是否为请求它的用户标记/标记/标记了项目,并且此信息在表格上设置,给出了项目和用户之间的关系。
Currently I'm fetching the Item, and then finding the reference - updating the property to true if the reference could be found. 目前我正在获取Item,然后查找引用 - 如果可以找到引用,则将属性更新为true。 Can I do this in one query instead? 我可以在一个查询中执行此操作吗?
var item = Session.Get<Item>(itemId);
var flaggedResult = Session.CreateCriteria<ItemWithUserFlag>()
.Add(Restrictions.Eq("User.Id", userId))
.Add(Restrictions.Eq("Item", item))
.List<ItemWithUserFlag>();
if (flaggedResult.Count > 0)
item.IsMarked = true;
return item;
How about using formula
along with filter
in your property mapping: 如何在属性映射中使用formula
和filter
:
<property name="IsMarked" formula="(select count(*) from ItemWithUserFlag where ItemWithUserFlag.ItemId = ItemId and ItemWithUserFlag.UserId = :UserFilter.userId)" />
And filter def: 并过滤def:
<filter-def name="UserFilter">
<filter-param name="userId" type="Int32"/>
</filter-def>
That will result in something like 这会产生类似的结果
SELECT Item.*, (select count(*) from ItemWithUserFlag where ItemWithUserFlag.ItemId = Item.ItemId and ItemWithUserFlag.UserId = ?) AS IsMarked FROM Item
As long as IsMarked is defined as bool
, if count(*)
returns 0
it will be converted to false
and if anything > 0
it will be converted to true
. 只要IsMarked被定义为bool
,如果count(*)
返回0
,它将被转换为false
,如果任何> 0
,它将被转换为true
。
EDIT: Fluent representation 编辑:流利的代表
public class ItemMap : ClassMap<Item>
{
public ItemMap()
{
/// ... whatever
Map(x => x.IsMarked).Formula("(select count(*) from ItemWithUserFlag where ItemWithUserFlag.ItemId = ItemId and ItemWithUserFlag.UserId = :UserFilter.userId)");
}
}
public class UserFilter : FilterDefinition
{
public UserFilter()
{
WithName("UserFilter")
.AddParameter("userId", NHibernate.NHibernateUtil.Int32);
}
}
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