I've come up with the following LINQ, but I can't help thinking that I should be able to do this in one query instead of two. Can anyone help?
The idea is to inner join three tables and group by one.
var q1 = from er in ExportRules
join per in PlaceExportRules on er.ExportRulesID equals per.ExportRulesID
select new
{
PlaceID = per.PlaceID,
Description = er.Description,
Tag = er.TagName,
ExportName = per.ExportName,
ExportAddress = per.ExportAddress
};
var q2 = from p in Places
join rules in q1 on p.PlaceID equals rules.PlaceID into joined2
where joined2.Any()
orderby p.PlaceName
select new {Place = new {p.PlaceID, p.PlaceName}, joined2};
Well, you can just bracket things:
var query = from p in Places
join rules from
(from er in ExportRules
join per in PlaceExportRules
on er.ExportRulesID equals per.ExportRulesID
...)
on p.PlaceId equals rules.PlaceId into joined2
where joined2.Any()
orderby p.PlaceName
select new {Place = new {p.PlaceID, p.PlaceName}, joined2};
However, I'd personally probably leave it as two queries. It's clearer, and won't affect the performance - it's not like the first statement in your code would actually execute the query.
Related
I am trying to do a left outer join on three tables. I know there is a way to do it in one variable but I haven't been able to figure it out. Instead I have performed two separate left outer joins and then did a left out join on those. Here is my code for that:
var outerJoin1 =
(from h in resultHours
join u in results on new {h.PhysicalUnitId, h.MonthNum} equals new {u.PhysicalUnitId, u.MonthNum} into outer
from grouping in outer.DefaultIfEmpty()
select new {timeKey = h, Key = grouping});
var outerJoin2 =
(from h in resultHours
join s in serviceHrsResults on new {h.PhysicalUnitId, h.MonthNum} equals new {s.PhysicalUnitId, s.MonthNum} into outer2
from grouping in outer2.DefaultIfEmpty()
select new {timeKey = h, Key = grouping});
var outerJoin =
(from a in outerJoin1
join b in outerJoin2 on new {a.timeKey.PlantId, a.timeKey.MonthNum} equals new {b.timeKey.PlantId, b.timeKey.MonthNum} into outer
from grouping in outer.DefaultIfEmpty()
select new{timeKey = a, Key = grouping}).Distinct();
I have tried putting the above together in one variable I can't get it to work. Here is what I have tried:
var outerjoin =
from h in resultHours
join u in results on new {h.PhysicalUnitId, h.MonthNum} equals new {u.PhysicalUnitId, u.MonthNum} into outer
from grouping in outer.DefaultIfEmpty()
from hr in resultHours
join s in serviceHrsResults on new {hr.PhysicalUnitId, hr.MonthNum} equals new {s.PhysicalUnitId, s.MonthNum} into outer2
from grouping in outer2.DefaultIfEmpty()
select new {timeKey = h && timeKey = hr, Key = grouping};
The problem with this is the two groupings conflict. i'm pretty sure I just need a single grouping right before the select but cannot figure out how to use the "grouping in" and include both outer.DefaultIfEmpty() and outer2.DefaultIfEmpty().
I would appreciate it if someone could enlighten me.
You are using duplicate range variable ids - you've got 2x grouping.
- Which grouping is it that you want in the result set ?
- What is this line expected to achieve?
timeKey = h && timeKey = hr - how do you want to combine those in the projection ?
I would try the query below, but I've changed the select part of it as your combined version doesn't make sense to me.
Let me know if it at all works for you as without data it's not easy to test this, so I can't be sure that the new version is fine.
var outerjoin =
from h in resultHours
join u in results on new {h.PhysicalUnitId, h.MonthNum} equals new {u.PhysicalUnitId, u.MonthNum} into outer
from grouping1 in outer.DefaultIfEmpty()
//from hr in resultHours
join s in serviceHrsResults on new {grouping1.PhysicalUnitId, grouping1.MonthNum} equals new {s.PhysicalUnitId, s.MonthNum} into outer2
from grouping2 in outer2.DefaultIfEmpty()
select new {timeKey = h, Key1 = grouping1, Key2 = grouping2};
I am trying to create an outer join statement in LINQ and am not having much luck. I know that Performing an outer join requires two steps:
(1) Convert the join into a group join with into
(2) Use DefaultIfEmpty() on the group to generate the null value you expect if the joined result set is empty.
I have been using this code as an example:
var query = (from p in dc.GetTable<Person>()
join pa in dc.GetTable<PersonAddress>() on p.Id equals pa.PersonId into tempAddresses
from addresses in tempAddresses.DefaultIfEmpty()
select new { p.FirstName, p.LastName, addresses.State });
So I tried to do this:
var outerJoin =
from h in resultHours
join u in results on h.Key equals u.Key into outer
from dictionary in outer.DefaultIfEmpty()
select new {
The problem is that intellisense doesn't recognize anything in the select new {} statement. I've tried u. and h., even dictionary.
The problem I may be running into is that I'm trying to outer join two dictionaries. It doesn't seem to like that, although this is what I was told I need to do. I am obviously doing something wrong or not understanding something.
I need to join the dictionary results.Unit with the dictionary resultHours.Hours because my output is missing unitId fields under certain conditions. Doing an outer join is supposed to clear this up.
Here is the code for results:
var results =
(from v in VDimUnit
join vf in VFactEnergyAllocation on v.UnitKey equals vf.UnitKey
join vd in VDimGadsEvent on vf.GadsEventKey equals vd.GadsEventKey
join vt in VDimTime on vf.TimeKey equals vt.TimeKey
where typeCodes.Contains(vd.GadsEventTypeCode)
&& vt.YearNum >= (year - 3) && vt.YearNum <= year
group vf by new {v.PlantId, v.PhysicalUnitId, v.NetDependableCapacity, v.NetMaximumCapacity,
vt.MonthNum} into groupItem
select new {groupItem.Key.PlantId, groupItem.Key.PhysicalUnitId, groupItem.Key.NetMaximumCapacity,
groupItem.Key.MonthNum, PO_HRS = groupItem.Sum(
x=> (float)x.AllocatedEnergyMwh / groupItem.Key.NetDependableCapacity),
UO_HRS = groupItem.Sum(x=> (float)x.AllocatedEnergyMwh / groupItem.Key.NetDependableCapacity),
Unit = groupItem.Count(), groupItem.Key}).ToDictionary(x=> x.Key, x=> x);
Here is the code for resultHours:
var resultHours =
(from vt in VDimTime
join vf in VFactEnergyAllocation on vt.TimeKey equals vf.TimeKey
join vd in VDimGadsEvent on vf.GadsEventKey equals vd.GadsEventKey
join v in VDimUnit on vf.UnitKey equals v.UnitKey
group vt by new {v.PlantId, v.PhysicalUnitId, v.NetDependableCapacity, v.NetMaximumCapacity,
vt.MonthNum} into groupItem
select new {groupItem.Key.PlantId, groupItem.Key.PhysicalUnitId, groupItem.Key.NetMaximumCapacity,
Hours = groupItem.Count(), groupItem.Key}).ToDictionary(x=> x.Key.ToString(), x=> x.Hours);
This is presently how I have my output. It will change after I figure out how to do the outer join.
var finalResults =
(from r in results
orderby r.Key.MonthNum, r.Key.PlantId, r.Key.PhysicalUnitId
select new {Site = r.Key.PlantId, Unit = r.Key.PhysicalUnitId, r.Key.MonthNum, Numerator = r.Value.PO_HRS, Denominator =
resultHours[r.Key.ToString()], Weight = r.Key.NetMaximumCapacity, Data_Indicator = DATA_INDICATOR,
Budgeted = budgetedPlannedOutageHrs, Industry_Benchmark = INDUSTRY_BENCHMARK, Comments = comments,
Executive_Comments = executiveComments, Fleet_Exec_Comments = fleetExecComments});
I'm at a loss. The LINQ outer join examples I have found apaprently do not apply when joining dictionaries.
I wonder if anyone can help
I have a simple SQL Query which was this.
SELECT * FROM ITEM INNER JOIN CODES ON ITEM.ITEMID = CODES.ITEMID AND
ITEM.CATID = CODES.CATID
This works great, so i created the following query in LINQ
from i in Item join c in codes
on new { i.itemid, i.catid } equals new { c.itemid, c.catid }
Works great, but they i realized that i actually needed an LEFT JOIN in place of the INNER JOIN. So the sql, which now works great!, is :- (notice left join)
SELECT * FROM ITEM LEFT JOIN CODES ON ITEM.ITEMID = CODES.ITEMID AND
ITEM.CATID = CODES.CATID
So now everything seems to work and i get back the data i require using SQL i can't figure out how to do a left join in LINQ and especially how to do a left join on more than 1 field - in my case itemid and catid
I wonder if anyone can lend a hand, i am stuck :-)
I think this is the direction you need to head down:
from i in Item
join c in codes on new { i.itemid, i.catid } equals new { c.itemid, c.catid }
into grouped
from g in grouped.DefaultIfEmpty()
select new
{
ItemId = c.itemid,
CatItemId = g != null ? g.itemid : "Empty"
};
You should look: http://codingsense.wordpress.com/2009/03/08/left-join-right-join-using-linq/
The key is -->
into JoinedEmpDept
from dept in JoinedEmpDept.DefaultIfEmpty()
I'm familiar with doing simple Many-to-Many relationships (i.e. simple joins) in Linq to SQL, but I'm having a hard time thinking right now.
I have three tables (and so, entities in my Linq-to-SQL model) representing a taxonomic system. Standard-issue really:
Products - ProductTags - Tags
I'm writing a method that returns a set of Products where the Tag they're in matches a query. So if someone searches for "foo" then all products assigned with the tags "foobar" or "fooqux" (but not "bazbar") would be returned.
I know I have to structure the query into two parts: first to get the matching Tags, and then to get the Products that have those tags. It's the second part I'm stumped on.
Here's what I've got so far:
var tags = from t in db.Tags
where t.Name.Contains( tagSearchQuery )
select t;
var products = from p in db.Products
// then a miracle happens
select p;
Assistance much appreciated :)
You can do it in one query if you just start with the ProductTags table. You'll probably also need a Distinct to avoid duplicate products matching multiple tags.
var products = (from pt in db.ProductTags
where pt.Tag.Name.Contains( tagSearchQuery )
select pt.Product).Distinct();
or here's another way:
var products = from p in db.Products
from pt in p.ProductTags
where pt.Tag.Name.Contains( tagSearchQuery )
select p
IQueryable<Tag> tags =
from t in db.Tags
where t.Name.Contains( tagSearchQuery )
select t;
IQueryable<Product> products =
from p in db.Products
where p.ProductTags.Any(pt => tags.Contains(pt.Tag))
select p;
OR
IQueryable<Product> products =
from p in db.Products
from pt in p.ProductTags
let t = pt.Tag
where t.Name.Contains( tagSearchFragment )
group t by p into g
select g.Key;
I have the following SQL query:-
select distinct * from dbo.Profiles profiles
left join ProfileSettings pSet on pSet.ProfileKey = profiles.ProfileKey
left join PlatformIdentities pId on pId.ProfileKey = profiles.Profilekey
I need to convert it to a LinqToEntities expression. I have tried the following:-
from profiles in _dbContext.ProfileSet
let leftOuter = (from pSet in _dbContext.ProfileSettingSet
select new
{
pSet.isInternal
}).FirstOrDefault()
select new
{
profiles.ProfileKey,
Internal = leftOuter.isInternal,
profiles.FirstName,
profiles.LastName,
profiles.EmailAddress,
profiles.DateCreated,
profiles.LastLoggedIn,
};
The above query works fine because I haven't considered the third table "PlatformIdentities". Single left outer join works with what I have done above. How do I include PlatformIdentities (the 3rd table) ? I basically want to translate the SQL query I specified at the beginning of this post (which gives me exactly what I need) in to LinqToEntities.
Thanks
Let me know if you want to select something different, but a true join is below
from p in _dbContext.ProfileSet
join ps in _dbContext.ProfileSettings on p.ProfileKey = ps.ProfileKey into a
join pi in _dbContext.PlatformIdentities on p.ProfileKey = pi.ProfileKey into b
select new
{
profiles.ProfileKey,
profiles.FirstName,
profiles.LastName,
profiles.EmailAddress,
profiles.DateCreated,
profiles.LastLoggedIn,
PlatformSettings = a.Select(x=>x),
PlatformIdentities = b.Select(y=>y)
}