I am trying to figure out the LINQ syntax for multiple left join, but I am getting the error: The name 'c' is not in scope on the left side of 'equals'. Consider swapping the expressions on either side of 'equals'.
I have already tried swapping, and if I do, it makes both 'c' and 'd' have the "not in scope" error.
var result =
from a in db.tableA
join b in db.tableB //first join (inner join)
on a.field1 equals b.field1
join c in db.tableC //second join (left join)
on a.field1 equals c.field1
into left_one
join d in db.tableD //third join (left join)
on c.field2 equals d.field2
// ^ here
into left_two
where a.field1 == theValueImSearchingFor
from c in left_one.DefaultIfEmpty()
from d in left_two.DefaultIfEmpty()
select new CombinedObject()
{
...
}
The reason I am using on c.field2 equals d.field2 in the third join statement is that my tables are structured like this:
tableA: field1
tableB: field1
tableC: field1 field2
tableD: field2
That is, the only way to relate tableD to the rest of the data is to use field2.
Can someone please correct my syntax? Or is there a certain way I have to do it given my setup of tables?
I use this type of syntax:
var results = (from a in db.tableA
from b in db.tableB.Where(s => s.field1 == a.field1)
from c in db.tableC.Where(s => s.field1 == a.field1).DefaultIfEmpty()
from d in db.tableD.Where(s => s.field2 == c.field2).DefaultIfEmpty()
select new CombinedObject() { });
It seems to work well on multiple tables. I think I got my field1s and field2s right to match your example :)
[Edit]
As per the comment, if you want to add in some additional filtering, you just add it in where appropriate into the Where(). Eg:
from c in db.tableC.Where(s => s.field1 == a.field1 && s.field3 == someVariable).DefaultIfEmpty()
Something like that :)
Related
I am trying to perform an outer join in C# using Linq, the person mentoring me keeps saying I shouldn't try to do an outer join which isn't really an answer.
What I got from the other threads is that I need the .DefaultIfEmpty() where ever I may not have a record.
I tried it first on just the lines where there may be a missing information then added it to every line just to see if that was the problem.
Every time I run this I get only the inner join records. It works great other than it is not including the two records from my DB that only have information in the first two tables.
var sqlQuery =
from s in ctx.Suppliers
from sp in ctx.SupplierParts
.Where(sp => sp.SupplierID == s.SupplierID)
.DefaultIfEmpty()
from sm in ctx.SupplierManufacturerRelations
.Where(sm => sm.SupplierPNID == sp.SupplierPNID)
.DefaultIfEmpty()
from mp in ctx.ManufacturerParts
.Where(mp => mp.MfgPNID.Equals(sm.MfgPNID))
.DefaultIfEmpty()
from m in ctx.Manufacturers
.Where(m => m.ManufacturerID.Equals(mp.ManufacturerID))
.DefaultIfEmpty()
from im in ctx.ItemMasters
.Where(im => im.PreID == mp.PreID)
.Where(im => im.PartNumber == mp.PartNumber)
.DefaultIfEmpty()
from c in ctx.ComponentClasses
.Where(c => c.CCID == im.CCID)
.DefaultIfEmpty()
from um in ctx.UnitsOfMeasures
.Where(um => um.UOMID == sp.UOMID)
.DefaultIfEmpty()
select new
{ my variables}
var querylist = sqlQuery.Where(n => n.SupplierID == thisSupplier).ToList();
I also tried
from s in ctx.Suppliers
join sp in ctx.SupplierParts on s.SupplierID equals sp.SupplierID
join sm in ctx.SupplierManufacturerRelations on sp.SupplierPNID equals sm.SupplierPNID into spartgroup
from sm in spartgroup.DefaultIfEmpty()
join mp in ctx.ManufacturerParts on sm.MfgPNID equals mp.MfgPNID into mpartgroup
from mp in mpartgroup.DefaultIfEmpty()
join m in ctx.Manufacturers on mp.ManufacturerID equals m.ManufacturerID into mgroup
from m in mgroup.DefaultIfEmpty()
join im in ctx.ItemMasters
on new { key1 = (int)mp.PreID, key2 = (int)mp.PartNumber }
equals new { key1 = im.PreID, key2 = im.PartNumber }
into tpartgroup
from im in tpartgroup.DefaultIfEmpty()
join c in ctx.ComponentClasses on im.CCID equals c.CCID into fullgroup
from c in fullgroup.DefaultIfEmpty()
join um in ctx.UnitsOfMeasures on sp.UOMID equals um.UOMID
This SQL query works and doesn't omit the rows
SELECT Supplier.SupplierID
, SupplierPart.SupplierPNID
, SupplierPart.SupplierPN
, SupplierPart.Description
, SupplierManufacturerRelation.MfgPNID
, ManufacturerPart.PreID
, ManufacturerPart.PartNumber
, ItemMaster.CCID
, ItemMaster.Description AS Expr1
FROM Supplier
Inner JOIN SupplierPart
ON Supplier.SupplierID = SupplierPart.SupplierID
Left JOIN SupplierManufacturerRelation
ON SupplierPart.SupplierPNID = SupplierManufacturerRelation.SupplierPNID
Left JOIN ManufacturerPart
ON SupplierManufacturerRelation.MfgPNID = ManufacturerPart.MfgPNID
Left JOIN ItemMaster
ON ManufacturerPart.PreID = ItemMaster.PreID
AND ManufacturerPart.PartNumber = ItemMaster.PartNumber
WHERE Supplier.SupplierID = 9
For translating SQL to LINQ query comprehension:
Translate FROM subselects as separately declared variables.
Translate each clause in LINQ clause order, translating monadic operators (DISTINCT, TOP, etc) into functions applied to the whole LINQ query.
Use table aliases as range variables. Use column aliases as anonymous type field names.
Use anonymous types (new { ... }) for multiple columns.
Left Join is simulated by using a into join_variable and doing another from from the join variable followed by .DefaultIfEmpty().
Replace COALESCE with the conditional operator and a null test.
Translate IN to .Contains() and NOT IN to !...Contains()
SELECT * must be replaced with select range_variable or for joins, an anonymous object containing all the range variables.
SELECT fields must be replaced with select new { ... } creating an anonymous object with all the desired fields or expressions.
Proper FULL OUTER JOIN must be handled with an extension method.
So from your SQL, your query should look like:
var ans = from s in ctx.Suppliers
join sp in ctx.SupplierParts on s.SupplierID equals sp.SupplierID
join sm in ctx.SupplierManufacturerRelations on sp.SupplierPNID equals sm.SupplierPNID into smj
from sm in smj.DefaultIfEmpty()
join mp in ctx.ManufacturerParts on sm?.MfgPNID equals mp.MfgPNID into mpj
from mp in mpj.DefaultIfEmpty()
join im in ctx.ItemMasters on new { key1 = (int)mp.PreID, key2 = (int)mp.PartNumber } equals new { key1 = im.PreID, key2 = im.PartNumber } into imj
from im in imj.DefaultIfEmpty()
select new {
s.SupplierID, sp.SupplierPNID, sp.SupplierPN, sp.Description, sm.MfgPNID, mp.PreID, mp.PartNumber, im.CCID, Expr1 = im.Description
};
Need some help in writing LINQ from the following SQL.
The main problem is double grouping.
I'm stacked in the second grouping
group by s.[e-year], s.[e-month]
Don't know how to implement.
Thanks a lot.
select s.[e-year], s.[e-month], count(s.projectid) 'projects entranced',
---------------------------------------------
(select count(subquery.CustomerTypeID) from
(select count(ap.ProjectID) as 'count', c.CustomerTypeID FROM Logging_ProjectsEntrances] pe
inner join users u on pe.userid = u.userid
inner join Companies c on u.CompanyId = c.CompanyID
inner join AssignedProjects up on pe.ProjectID = up.ProjectID
inner join Projects p on up.ProjectID = p.ProjectID
where ap.ProductID = 1 and year(pe.EntranceDate) = s.[e-year] and MONTH(pe.entrancedate) = s.[e-month] and c.CustomerTypeID = 2
group by ap.ProjectID, c.CustomerTypeID) subquery
group by subquery.CustomerTypeID
)
--------------------------------------------
from
(
select YEAR(pe.EntranceDate) as 'e-year', MONTH(pe.EntranceDate) as 'e-month', up.ProjectID as 'projectid'
FROM Logging_ProjectsEntrances pe
inner join AssignedProjects ap on pe.ProjectID = ap.ProjectID
inner join Projects p on ap.ProjectID = p.ProjectID
where ap.ProductID = 1
group by year(pe.EntranceDate), month(pe.EntranceDate), ap.ProjectID
) as s
group by s.[e-year], s.[e-month]
order by s.[e-year] desc , s.[e-month] desc
For translating SQL to LINQ query comprehension:
Translate FROM subselects as separately declared variables.
Translate each clause in LINQ clause order, translating monadic operators (DISTINCT, TOP, etc) into functions applied to the whole LINQ query.
Use table aliases as range variables. Use column aliases as anonymous type field names.
Use anonymous types (new { ... }) for multiple columns.
Left Join is simulated by using a into join_variable and doing another from from the join variable followed by .DefaultIfEmpty().
Replace COALESCE with the conditional operator and a null test.
Translate IN to .Contains() and NOT IN to !...Contains()
SELECT * must be replaced with select range_variable or for joins, an anonymous object containing all the range variables.
SELECT fields must be replaced with select new { ... } creating an anonymous object with all the desired fields or expressions.
Proper FULL OUTER JOIN must be handled with an extension method.
Note: Your SQL query is using a SQL trick (SELECT x ... GROUP BY x) to perform the equivalent of a DISTINCT, which should be used as it expresses the intent more clearly.
So, for your SQL query:
var subq = (from pe in projectsEntrances
join ap in assignedProjects on pe.ProjectID equals ap.ProjectID
join p in projects on ap.ProjectID equals p.ProjectID
where ap.ProductID == 1
select new { e_year = pe.EntranceDate.Year, e_month = pe.EntranceDate.Month, ap.ProjectID }).Distinct();
var ans = from s in subq
group s by new { s.e_year, s.e_month } into sg
orderby sg.Key.e_year descending, sg.Key.e_month descending
select new { sg.Key.e_year, sg.Key.e_month, ProjectsEntranced = sg.Count() };
I want to convert this SQL code to LINQ. Here is my SQL code:
SELECT Rooms.RoomName AS RoomNo, Beds.BedName AS Beds, Rooms.RoomType, ISNULL(CheckIn.CheckIntatus,'') AS Status
FROM CheckIn
INNER JOIN GuestBeds ON CheckIn.GuestBedId = GuestBeds.Id
AND (CheckIn.CheckInStatus = 1 OR CheckIn.CheckIntatus = 2 OR CheckIn.CheckSIntatus = 3)
RIGHT JOIN Beds ON GuestBeds.BedId = Beds.Id
INNER JOIN Rooms ON Beds.RoomId = Rooms.Id
LEFT JOIN Guests ON CheckIn.GuestId = Guests.Id
WHERE Beds.Active = 1 AND Rooms.Active = 1
ORDER BY RoomName, Beds
It works well which means it shows all the RoomName with CheckInStatus. If the Room is not presence in CheckIn table, ot will return the status as Null.
So I want to convert the code to LINQ. SO here is my LINQ code:
from b in Beds
join w in Rooms on b.RoomsId equals w.Id
where (a.CheckInStatus == 3 || a.CheckInStatus == 1 || a.CheckInStatus == 2)
join p in GuestBeds on b.Id equals p.BedId
join a in CheckIn on p.Id equals a.GuestBedId
join t in Guests on a.GuestId equals t.Id
where b.Active == true && w.Active == true
orderby w.RoomName
select new
{
RoomName = w.RoomName,
BedName = b.BedName,
Status = a.CheckInStatus
}
It didnt worked like the first code. It only show the data which contain CheckInStatus. I want it to show all the RoomName inside Room database
Normally I would post some rules for converting SQL to LINQ but this is complicated enough I think I'd need to make new rules. I commented out the references to Guests because as a LEFT JOIN it has no bearing on the answer.
Pull out the WHERE on individual tables and make them sub-queries:
var ActiveBeds = Beds.Where(b => b.Active == 1);
var ActiveRooms = Rooms.Where(r => r.Active == 1);
In LINQ, a RIGHT JOIN must be done by flipping the join to be a left join, so we will create the two sides as sub-queries.
Left side of RIGHT JOIN:
Translate the JOIN conditions that aren't part of an equi-join into a LINQ where clause on the appropriate tables (alternately this could be a subquery as above). The LEFT JOIN becomes a LINQ join/from ... DefaultIfEmpty() phrase, but as noted above isn't needed.
var CheckInsGuestBedsGuests = from c in CheckIn
where (c.CheckInStatus == 1 || c.CheckInStatus == 2 || c.CheckInStatus == 3)
join gb in GuestBeds on c.GuestBedId equals gb.Id
//join g in Guests on c.GuestId equals g.Id into gj
//from g in gj.DefaultIfEmpty()
select new { c, gb /*, g */ };
Right side of RIGHT JOIN:
The other side of the RIGHT JOIN includes an INNER JOIN so put them together in a sub-query:
var ActiveBedsRooms = from b in ActiveBeds
join r in ActiveRooms on b.RoomId equals r.Id
select new { b, r };
Finally, flip the sub-queries to create a left join using the same idiom as above:
var ans = from br in ActiveBedsRooms
join cgbg in CheckInsGuestBedsGuests on br.b.Id equals cgbg.gb.BedId into cgbgj
from cgbg in cgbgj.DefaultIfEmpty()
select new {
RoomNo = br.r.RoomName,
Beds = br.b.BedName,
br.r.RoomType,
Status = cgbg.c.CheckInStatus
};
NOTE: If you were not using LINQ to SQL, the Status expression would fail when cgbg is null and you would need
Status = cgbg?.c.CheckInStatus
but unfortunately LINQ to SQL/EF doesn't handle the null conditional operators yet.
BTW, nice query - brings back memories of when I used to write hotel front desk software :)
this is a bit confusing for me. I know that left outer joins aren't built in to LINQ natively and that you have to use 'into' and 'DefaultIfEmpty()', but I have a bit of a complex SQL query.
The query:
SELECT * FROM TableA as a
LEFT OUTER JOIN TableB as b
on a.ID = b.ID and a.StatusOne = 1 AND b.StatusOne = 1 AND (a.StatusTwo != 1 OR b.StatusTwo!= 1)
LEFT OUTER JOIN TableC as c
on a.ID = c.ID AND a.StatusOne = 1 AND c.StatusOne = 1 AND (a.StatusTwo != 1 OR c.StatusTwo != 1)
WHERE
a.ID = 99999 AND (b.ID is not null OR c.ID is not null)
I'm not even really sure where to begin on this. If someone could help me out I would appreciate it immensely.
I am giving you the idea behind, I didn't tested the code, but to join two tables based on different fields, your join should have a anonymous type to compare.
var one = 1
from a in tableA
join b in tableB on new { a.ID, b.StatusOne } equals new { b.ID, one} into ab
But in your case you have more than one condition, so before calling DefaultIsEmpty, you should check the latest condition
from a in tableA
join b in tableB on new { a.ID, b.StatusOne } equals new { b.ID, one} into ab
from ab in ab.Where(x => x.a.StatusTwo != 1 || x.b.StatusTwo != one).DefaultIfEmpty()
Then the other outer join follows the same pattern and you need to make a final join. A good way to start is downloading the LinqPad and see which lambda expression it generates for your query, and you can take it from there. You can optimize it later but you will get the idea behind the generation. Hope this helps
How can I join two different tables based on a condition?
I have my query as under:
var myquery = from p in db.tbl1
join q in db.tbl2 on p.field1 equals q.field1
join r in db.tbl3 on q.field2 equals r.field2
Till here everything is fine, now I want to add 1 more join to a table but it should be based on a condition like:
if(q.field3 == 1)
join s in db.tbl4 on q.field4 equals s.field4
else if(q.field3 == 2)
join s in db.tbl5 on ....
So basically I want to join to different tables based on the value of q.field3.
You're not going to be able to conditionally join based on the value of a single row. The idea of joining is that you're joining based off of all of the rows. Conditionally determining what/how to join based on some value outside of the query would make sense.
What you can do is do both joins unconditionally, but choose which result to use conditionally for each row. Obviously this will only work if the tables are of the same type, or if you first project s1 and s2 into a common type (using let)
var myquery = from p in db.tbl1
join q in db.tbl2 on p.field1 equals q.field1
join r in db.tbl3 on q.field2 equals r.field2
join s1 in db.tbl4 on q.field4 equals s1.field4
join s2 in db.tbl5 on q.field5 equals s2.field5
let s = q.field3 == 1 ? s1 :
q.field3 == 2 ? s2 : null
This should be able to be translated by the query provider into a CASE statement.