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Simplifying LINQ query in C#

Table1
Table1ID Name Graduation Version Hobbies
1 A Degree 1 B
2 A Degree 2 C
3 A Degree 3 D
Table2
Table2ID Table1ID Name Graduation Version Address Surname Date
1 1 A Degree 1 A A 08-10-2019
2 2 A Degree 2 A A 08-10-2019
3 3 A Degree 3 A A
//I want to check if any version greater than highest version exists in Table1 .where Date column is not null in Table2
Suppose for the combination of Name and Degree , the highest version is 2 in Table2 since Date is null for Table2, I want to check if any record greater than 2 exists in Table1, if yes add it to a new List
Here is what I am doing.
List<Table2> groupByTable2 = //Operations on Table2 and get highest Version record from db
List<Table1> check = new List<Table1>();
List<Table1> check2 = await _table1.GetAll().ToListAsync();
Foreach(var a in groupByTable2)
{
List<Table1> check4 = check2.Where(x => x.Name == a.Name && x.Graduation == a.Graduation).ToList();
If(check4.Any(x=>x.Version > a.Version))
{
check.Add(check2.Where(x=>x.Table1ID == a.Table1ID).First());
}
}
Now my check contains a record where ID is 3. But is there any simpler way to achieve this in simpler way with readability and performance?

I hope I understood what you are trying to achieve. You could try the following.
var result = table2.Where(x=>x.Date!=null)
.GroupBy(x=> new {x.Name, x.Graduation})
.SelectMany(x=> x.OrderByDescending(c=>c.Version).Take(1))
.Join(table1,t2=>t2.Table1ID,t1=>t1.Table1ID,(t2,t1)=>t1)
.ToList();
result.AddRange(table1.Where(x=> result.Any(c=>c.Name.Equals(x.Name)
&& c.Graduation.Equals(x.Graduation)
&& c.Version < x.Version)));
The idea is to first use GroupBy and Join to get the List of Items with highest Version number in Table1 that has a valid date in Table2. Then, use List.AddRange to add remaining higher versions from Table1.

When returning the count from SQL, how to also include the value in grouped item for which the count doesn't exist?

Been working on this SQL dilemma for a while now. The part of the table looks like the following.
It's a many-to-many table relationship where one claim can have many notes. So, one example would be the following:
------------------------------------------
| ClaimID | NoteID | Note |
------------------------------------------
| 2387 | 1 | Test 1 |
| 2387 | 2 | Test 2 |
| 2387 | 3 | Test 3 |
| 2532 | 4 | Something 1 |
| 2539 | 5 | abcd |
| 2539 | 6 | jklm |
------------------------------------------
You get the idea.
So, when I run the query I want the result in such a way that it should show me the number of note counts from 1 to 10. If the count exist, then it should show me the count, otherwise 0. An example of what it would look like in the real-world scenario is the following.
[{
"numOfNotes":1,
"count":5916
},{
"numOfNotes":2,
"count":1846
},{
"numOfNotes":3,
"count":639
},{
"numOfNotes":4,
"count":226
},{
"numOfNotes":5,
"count":94
},{
"numOfNotes":6,
"count":50
},{
"numOfNotes":7,
"count":10
},{
"numOfNotes":8,
"count":2
},{
"numOfNotes":9,
"count":2
},{
"numOfNotes":11,
"count":2
}]
That's the query return from the database that I retrieved using C# and linq. Here's the code for that.
if (type == "e" || type == "p")
{
//sub query to retrieve notes
var subquery = from f in db.DBFileInfo
join c in db.Claims on f.FileID equals c.FileID into cl
from gp1 in cl.DefaultIfEmpty()
join n in db.Notes on gp1.ClaimID equals n.ClaimID into nt
from gp2 in nt.DefaultIfEmpty()
where f.ReportDate.Month == month && f.ReportDate.Year == year
group gp2 by gp2.ClaimID into g
select new
{
Key = g.Key,
Count = g.Count()
};
//query to grop by notes count. Notes count is consider contact per claim
var count = (from c in db.Claims
join s in subquery on c.ClaimID equals s.Key
where c.RecordType == type &&
(c.Username != "RxService")
&& (c.HIC3 != "J3A" && c.HIC3 != "J3C" && c.HIC3 != "H7N")
group s by s.Count into g
orderby g.Key
select new
{
NumOfNotes = g.Key,
count = g.Count()
}).Take(10);
}
If you notice in the result, there are numOfNotes from 1 - 11 but 10 is missing. That's because there aren't any claimID that has 10 notes. So, in this case, I still want SQL to return "numOfNotes": 10, "count": 0. And if you notice, I only asked for 10 results (Take(10)), because there can be more than 10 such notes per claim which we are not interested.
And in some cases, there aren't more than 5 notes per claimID for the given time period. In one instance, the result from SQL only goes up to 6. But I still want the result upto 10 whether it exists or not. Is it possible?
In case if you're interested: Here's my SQL statement
SELECT
count(C.ClaimID) as count, N.NotesPerClaim
FROM
ClaimsTable C
INNER JOIN
(SELECT
claimid, count(note) as NotesPerClaim
FROM
NotesTable
GROUP BY
ClaimID) as N ON N.ClaimID = C.ClaimID
WHERE
RecordType = 'e' AND
(Username <> 'RxService') AND
(HIC3 <> 'J3A' AND HIC3 <> 'J3C' AND HIC3 <> 'H7N')
GROUP BY
N.NotesPerClaim
ORDER BY
N.NotesPerClaim;

You seem to want a numbers table. Here is one method:
WITH nums as (
SELECT 1 as n
UNION ALL
SELECT n + 1
FROM nums
WHERE n < 10
),
t as (
SELECT count(C.ClaimID) as NumClaims, N.NotesPerClaim
FROM ClaimsTable C JOIN
(SELECT claimid, count(note) as NotesPerClaim
FROM NotesTable
GROUP BY ClaimID
) N
ON N.ClaimID = C.ClaimID
WHERE c.RecordType = 'e' AND
c.Username <> 'RxService' AND
c.HIC3 NOT IN ('J3A', 'J3C', 'H7N')
GROUP BY N.NotesPerClaim
)
SELECT nums.n as NotesPerClaim, t.NumClaims
FROM nums LEFT JOIN
t
ON nums.n = t.NotesPerClaim
ORDER BY NotesPerClaim;

Use LEFT JOIN instead of INNER JOIN
Also is better use HIC3 NOT IN ('J3A', 'J3C', 'H7N')
SELECT count(C.ClaimID) AS count
, N.NotesPerClaim
FROM ClaimsTable C
LEFT JOIN (
SELECT claimid
, count(note) AS NotesPerClaim
FROM NotesTable
GROUP BY ClaimID
) AS N ON N.ClaimID = C.ClaimID
WHERE RecordType = 'e'
AND (Username <> 'RxService')
AND HIC3 NOT IN ('J3A', 'J3C', 'H7N')
GROUP BY N.NotesPerClaim
ORDER BY N.NotesPerClaim;

LEFT JOIN on the notes table, and check for ISNULL condition. In the case of NULL from notes, return 0.
Here is a SQL Fiddle demo of the concept.
Your code should be:
`SELECT count(C.ClaimID) as count, ISNULL(N.NotesPerClaim,0) as NotesPerClaim
FROM ClaimsTable C
LEFT OUTER JOIN
(SELECT claimid, count(note) as NotesPerClaim from NotesTable
GROUP BY ClaimID) as N
ON N.ClaimID = C.ClaimID
WHERE RecordType = 'e' AND
(Username <> 'RxService') AND (HIC3 NOT IN ('J3A','J3C','H7N'))
GROUP BY ISNULL(N.NotesPerClaim,0)
ORDER BY N.NotesPerClaim;`

Not a simple Max

I have the following data:
Id | Value | OtherStuff
---------------------------
6 | 6 | 1
---------------------------
5 | 4 | 2
---------------------------
5 | 2 | 3
The desired result:
Id | Value | OtherStuff
---------------------------
6 | 6 | 1
---------------------------
5 | 4 | 2
That is I need the Max Value for each of the Id's.
I'm a bit stumped of how to do this without breaking it into multiple queries, can it be done, and if so how?
Update: I think I oversimplified the issue:
var query = from st in StockStakes
join o in Organisations on j.OrganisationId equals o.OrganisationId into oGroup
from o in oGroup.DefaultIfEmpty()
where st.Stock.Status == "A"
select new
{
Id = st.Id,
Value = st.Value,
CustomerId = o.OrganisationId
};
The data sample from above still stands... now how do i structure the query to give me the Max Value alongside each Id?

var query = from x in data
group x by x.Id into x
select x.OrderByDescending(y => y.Value).FirstOrDefault()
Based on you updated query, similar approach to the first query, but since you have multiple tables you need to group all the tables into an anonymous object and then select only the columns you want
var query = from st in StockStakes
join o in Organisations on j.OrganisationId equals o.OrganisationId into oGroup
from o in oGroup.DefaultIfEmpty()
where st.Stock.Status == "A"
group new { st, o } by st.Id into g
let largestValue = g.OrderByDescending(x => x.Value).FirstOrDefault()
select new
{
Id = g.Key,
Value = largestValue.st.Value,
CustomerId = largestValue.o.OrganisationId
};

I'm not really sure about what you mean, but maybe you can try with this query.
select Id, max(Value)
from your_table
group by Id;
This gives you the max "Value column" value for each "Id column" value.
-- EDIT --
LINQ version:
var q = from t in dc.YourTable
group t by t.Id
into g
select new
{
Id = g.Id,
Value = (from t2 in g select t2.Value).Max()
};
Code not tested. I'm on the bus now... :-) Give it a try!

The best way to Complex query in linq

The best way to change below in Linq Lamda
Category will be unique across Location to its base location. And I should load the category of immediate location first. If there is no category with that name then should load its immediate parent. Also I have 3 level in location.
Id Name Location
==========================
1 Breakfast India
2 Breakfast TamilNadu
3 Breakfast Chennai
4 Dinner India
5 Dinner TamilNadu
6 Lunch Chennai
7 Combo TamilNadu
(India -1 level, TamilNadu -2 level, Chennai -2 level)
And I need result as
3 Breakfast Chennai
5 Dinner TamilNadu
6 Lunch Chennai
7 Combo TamilNadu
My SQL Query is :
Declare #locationId UNIQUEIDENTIFIER = '7504657E-FEE4-E411-9505-BC305BB6199F'
BEGIN
DECLARE #Locations TABLE(Id UNIQUEIDENTIFIER,LocationLevel int)
Set NoCount On
INSERT INTO #Locations
SELECT AccountId,0 FROM Locations WHERE id = #locationId AND AccountId is not null
UNION
SELECT FranchiseId,1 FROM Locations WHERE id = #locationId AND FranchiseId is not null
UNION
SELECT #locationId,2
Set NoCount Off
SELECT C.*
FROM Categories c
Join #Locations l on c.LocationId = l.Id
WHERE c.IsDeleted = 0
AND (c.LocationId = #locationId OR (c.IsPublished = 1 And c.Status = 1))
AND l.LocationLevel =
(
Select Max(l1.LocationLevel)
From Categories c1
JOIN #Locations l1 on c1.LocationId = l1.Id
WHERE c1.Name=c.Name AND c1.IsDeleted = 0
)
Order by C.Name
END
My current query was :
var categoryes = await CategoryRepository.GetCategoryForContext(ParentLocationIdList.Keys);
Here ParentLocationIdList contains location id and level(1|2|3) for selected location
var result = categoryes.Join(ParentLocationIdList, c => c.LocationId, l => l.Key, (c, l) => new
{
Category = c,
Level = l.Value,
Name = c.Name
});
categoryes = result.GroupBy(g => g.Name).Select(s => s.First(d => d.Level == s.Max(m => m.Level)).Category).ToList();
return categoryes;

LINQ to SQL - CASE statement with subquery

I am having trouble trying to represent the below SQL (which returns the results I want) in LINQ:
select
case r.CategoryID
when 2 then
case r.PrimaryRecord
when 1 then r.RecordID
else (select RecordID from Record where RecordGroupID = r.RecordGroupID and PrimaryRecord = 1)
end
else
r.RecordID
end
as RecordID
, r.FooID
from Record r
where
r.FooID = 3
Each row in the Record table has a unique RecordID. Multiple RecordID's could be associated with a RecordGroupID for CategoryID 2, but only one of them will have the PrimaryRecord field value of 1.
Given the below table of data, my desired output is RecordID = 1, FooID = 3, i.e. the RecordID for the given RecordGroupID that is the PrimaryRecord, but the FooID for the given row that matches my Where clause.
RecordID RecordGroupID PrimaryRecord CategoryID FooID
1 1 1 2 1
2 1 0 2 1
3 1 0 2 3
I appreciate the SQL itself probably isn't the most efficient SQL in the world but it was the best I could come up with.
If anyone could help me create the LINQ statement to represent this query that would be great.

I think you don't really need the case in the original query. Try something like:
var matchingRecords = from r in Records
where r.FooId = fooId && r.CategoryId == catId && r.RecordGroupId == groupId
join r2 in Records on r.RecordGroupId == r2.RecordGroupId && r.CategoryId == r2.CategoryId && r2.PrimaryRecord
select r2;
Edit: added CategoryId in join, assuming RecordGroupId is only unique inside a category.