Outer right join doesn't work in NHibernate - mysql

Question

So I'm having two tables:
Table 1:
Item
id : int
title : varchar
comments : varchar
Table 2:
Rating
id : int
isUpvote : bit
date : datetime
item_id : int
One Item can have several ratings. IsUpvote states whether a Rating is a like or dislike.
I'm using NHibernate to ORM to my MySQL-database.
Want I want to make a kind of trending list of items to show which items have had to most likes in the past time (so from dateTime X to now).
The MySQL code looks like this:
select p.id, sum(case when r.isUpvote = b'1' then 1 else 0 END) - sum(case when r.isUpvote=b'0' then 1 else 0 END) as score
from rating as r
right join item as p
on p.id = r.item_id
group by p.id
order by score desc
limit 7;
This results in:
Id - Score
1 - 2
2 - 1
3 - 0
4 - 0
5 - 0
6 - 0
7 - 0
So I want to do this in NHibernate. I tried but HQL and QueryOver but I just can't figure it out. What I tried is:
GetTrendingItems(int nrOfTrendingItems, DateTime fromDate) {
var trendingItems = Session
.CreateQuery(#"select p, sum(case when r.IsUpvote = 1 then 1 else 0 END) - sum(case when r.IsUpvote=0 then 1 else 0 END) as score
from Item as p, Rating as r
where p.Id = r.Point.Id
group by p.Id
order by sum(case when r.IsUpvote = 1 then 1 else 0 END) - sum(case when r.IsUpvote=0 then 1 else 0 END) desc")
.SetMaxResults(nrOfClimbers)
.List();
}
and I tried:
GetTrendingItems(int nrOfTrendingItems, DateTime fromDate) {
DBRating dbRatingAlias = null;
var iets = Session.QueryOver<DBRating>(() => dbRatingAlias)
.Where(r => r.Date > fromDate)
.OrderBy(Projections.Conditional(
Restrictions.Where(() => dbRatingAlias.IsUpvote),
Projections.Constant(1),
Projections.Constant(-1))).Desc
.Right.JoinQueryOver<DBPoints>(r => r.Point)
.Take(nrOfClimbers)
.List();
}
I'm kinda losing hope here. Can someone help me?
Update:
The HQL generates this SQL:
select
dbpoints0_.id as col_0_0_,
sum(case
when dbrating1_.isUpvote=1 then 1
else 0
end)-sum(case
when dbrating1_.isUpvote=0 then 1
else 0
end) as col_1_0_,
dbpoints0_.id as id3_,
dbpoints0_.active as active3_,
dbpoints0_.title as title3_,
dbpoints0_.comments as comments3_,
dbpoints0_.score as score3_
from
points dbpoints0_,
Rating dbrating1_
where
dbpoints0_.id=dbrating1_.points_id
group by
dbpoints0_.id
order by
sum(case
when dbrating1_.isUpvote=1 then 1
else 0
end)-sum(case
when dbrating1_.isUpvote=0 then 1
else 0
end) desc limit ?p0;
?p0 = 10 [Type: Int32 (0)]
and the Fluent generates this SQL:
SELECT
this_.id as id6_0_,
this_.owners_id as owners2_6_0_,
this_.points_id as points3_6_0_,
this_.isUpvote as isUpvote6_0_,
this_.date as date6_0_
FROM
Rating this_
WHERE
this_.date > ?p0
ORDER BY
(case
when this_.isUpvote = ?p1 then ?p2
else ?p3
end) desc limit ?p4;
?p0 = 25-5-2015 22:39:49 [Type: DateTime (0)],
?p1 = True [Type: Boolean (0)],
?p2 = 1 [Type: Int32 (0)],
?p3 = -1 [Type: Int32 (0)],
?p4 = 10 [Type: Int32 (0)]

Answer 1

I made a stored procedure in de MySQL database
DELIMITER //
create procedure getTrending
(IN $getClimbers bool,
IN $fromDate DateTime,
IN $nrOfTrending int)
Begin
if ($getClimbers) then
select p.id, p.active, p.title, p.comments,
sum(case when r.isUpvote = b'1' and r.date > $fromDate then 1 else 0 END) - sum(case when r.isUpvote=b'0' and r.date > $fromDate then 1 else 0 END) as score
from rating as r
right join points as p
on p.id = r.points_id
group by p.id
order by sum(case when r.isUpvote = b'1' and r.date > $fromDate then 1 else 0 END) - sum(case when r.isUpvote=b'0' and r.date > $fromDate then 1 else 0 END) desc
limit $nrOfTrending;
else
select p.id, p.active, p.title, p.comments,
sum(case when r.isUpvote = b'1' and r.date > $fromDate then 1 else 0 END) - sum(case when r.isUpvote=b'0' and r.date > $fromDate then 1 else 0 END) as score
from rating as r
right join points as p
on p.id = r.points_id
group by p.id
order by sum(case when r.isUpvote = b'1' and r.date > $fromDate then 1 else 0 END) - sum(case when r.isUpvote=b'0' and r.date > $fromDate then 1 else 0 END) asc
limit $nrOfTrending;
end if;
end //
DELIMITER ;
and then called it from my C#-code with:
public virtual List<DBPoints> GetClimbers(int nrOfClimbers, DateTime fromDate)
{
OpenSession();
var query = Session.GetNamedQuery("getTrending");
query.SetBoolean("getClimbers", true);
query.SetDateTime("fromDate", fromDate);
query.SetInt32("nrOfTrending", nrOfClimbers);
var pointList = query.List<DBPoints>();
CloseSession();
return pointList.ToList();
}
For Nhibernate there needs to be made a mapping like this:
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
assembly="TechDash.Business"
namespace="TechDash.Business.Models.Database">
<sql-query name="getTrending">
<return class="DBPoints" />
call getTrending(:getClimbers, :fromDate, :nrOfTrending)
Since the names of my columns that are returned are the same as those that are returned when I'm retrieving a Points-object, I don't have to make a new C#-object nor the mapping belonging to that C#-object.