I have two tables and I am joinning them using linq query
TableA with columns ID and Name
TableB with columns ID, TableAID and Order
TableB's column TableAID is a link between TableA and TableB. Please note that TableB my contain rows that do not exist in TableA
My data is as under
TableA
ID Name
1 One
2 Two
3 Three
TableB
ID TableAID Order
1 1 2
2 2 1
3 4 1
4 5 1
In my linq query I want to select all rows from TableB with matching ID in TableA but the list should contain Name from TableA in the order of TableB. So my data should be
Two
One
Please help in building the linq statement
I have tried as below, but dont know where to put the order
var MyList = TableA.Where(x => TableB.Any(y => y.TableAID == x.ID))
.ToList();
Probably your query will be like as given below example,
var data = (from a in context.TableA
from b in context.TableB
where a.ID == b.TableAID
select new
{
a.Name,
b.Order
}).Distinct().OrderByDescending(x => x.Order).ToList();
foreach(var item in data)
{
Console.WriteLine(item.Name);
}
Alternatively, you can rewrite #M. Nasser Javaid answer in:
context.TableA.Join(context.TableB, a => a.ID, b => b.TableAID,
(a, b) => new {a.Name, b.Order}).Distinct()
.OrderByDescending(x => x.Order)
.Select(x => x.Name).ToList()
please try this:
var listresult = (from b1 in TableA
join a1 in TableB on b1.ID equals a1.TableAID
select new
{
b1.Name,
a1.Order
}).ToList().OrderByDescending(x=>x.Order);
var final = (from m in listresult
select m.Name).ToList();
Related
In my model, there are entities Article and Tag in many-to-many relation through table ArticleTag.
I want to select "trending tags" - tags with most articles in last X days, and I want this count too.
Basically, I need help creating EF Linq query equivalent to this SQL query, with ideal result being Dictionary<Tag, int>
SELECT TOP 50
t.Id, t.Name, count(*)
FROM ArticleTag at
JOIN Article a ON a.Id = at.ArticleId
JOIN Tag t ON t.Id = at.TagId
WHERE a.DateCreated > '2019-10-01'
GROUP BY t.Id, t.Name
ORDER BY count(*) DESC
Can this be done without having ArticleTag as DbSet in DbContext (since it is not really an entity, and I dont need it besides this query).
You have to use navigation properties for this query and do not need to know anything about ArticleTag table.
var query =
from a in ctx.Articles
from t in a.Tags
where a.DateCreated > someDate
group t by new { t.Id, t.Name } into g
orderby g.Count() descending
select new
{
g.Key.Id,
g.Key.Name,
Count = g.Count()
};
var result = query
.Take(50)
.ToDictionary(x => new Tag { Id = x.Id, Name = x.Name }, x => x.Count);
There are A and B tables that are related to each other. I want to create a linq query that will update the Status value in the A table if the entire row of relationship lines with the AID column in the B table is equal to or smaller than today's date in the Date field.
For example, according to the table below, the Status values of the rows with ID value 1 (AAA) and 2 (BBB) in Table A will be 1. Its Status value will not change because the line with ID value 3 (CCC) is not smaller than the current date of all the related rows in the B table.
How can I write the most stable and performance linq query?
Today : 2018-7-10
A Table
ID Name Status
1 AAA 0
2 BBB 0
3 CCC 0
B Table
ID AID Date
6 1 2018-5-3
7 2 2018-6-2
8 2 2018-6-4
9 3 2018-10-12
10 3 2018-7-7
Grouping TableB on AID
Selecting the "Max" date in each group.(Each unique AID)
Compares the selected dates with the corresponding Id in Table A.
Sets the Status value to true if the date is less or equal to the current date.
TableB.GroupBy(x => x.AId).Select(group => new { identifier = group.Key, MaxDate = group.Max(m => m.Date) }).ToList().ForEach(y =>
{
if (y.MaxDate <= DateTime.Now.Date)
{
TableA.Where(g => g.Id == y.identifier).First().Status = true;
}
});
This will select AIDs from Table B where Date is samller than now.
we select records from table A where its ID is in List from
previous step
Then we update Status value
A.Where ( a => B.Where( b => b.Date <= DateTime.Now).Select(b => b.AID).Contains(a.ID)).ForEach( a => a.Status = 1 )
/*Fetching those aS Who meet the condition. */
var aList1=(from b in dbset.Bs.Where(x=>x.Date<DateTime.Now)//TimeZone may vary
join a in dbSet.As
on b.AID equals a.ID
select a);
/*Fetching those aS Who don't meet the condition. */
var aList2=(from b in dbset.Bs.Where(x=>x.Date>=DateTime.Now)//TimeZone may vary
join a in dbSet.As
on b.AID equals a.ID
select a);
/*Removing those aS from list1 which occured in list2 */
var aFinalList=(aList1.Except(aList2)).ToList();
/*Updating status */
aFinalList.ForEach(x=>x.Status=1);
aFinalList.SaveChanges();
You can use GroupJoin extension in Lambda to Join the A and B tables then use All extension with your condition (date <= Today or any condition) then update the Status. Something like,
var lstResult = lstA.GroupJoin(lstB, a => new { a.Id }, b => new { Id = b.AId }, (a, b) => new { a, b })
.Select(x =>
{
if (x.b.All(y => y.Date <= DateTime.Now)) //Actual condition here.
{
x.a.Status = true;
return x.a;
}
else return x.a;
});
C# fiddle with sample data.
I have to retrieve all the columns from table1 and matching columns from table2. I have a stored procedure as :
alter Procedure [dbo].[usp_Property]
#UserId bigint =null
As
Begin
select P.PID, P.PropertyName, P.SBUArea, P.ListedOn,
P.Availability, P.Price, F.UserID, F.PID as FavProjId
from dbo.Property P left outer join dbo.Favorite F
on (F.PID=P.PID And F.UserID=#UserId)
I want to get Linq query for the same. So far I tried with something like
//User Id comes from session..
//var userId
var result=(from p in Properties
join f in Favorites
on p.PID equals f.PID into r
from r1 in r.DefaultIfEmpty()
where r1.UserID==userId
select new
{
p.PID,
p.PropertyName,
p.SBUArea, p.ListedOn,
r1.UserId
});
Can anyone please correct me. I want to use left outer join or any other alternate thing here.
If I beautify your SP's code, I get this:
DECLARE #UserId int
SET #UserId = 12435
SELECT
P.PID
,P.PropertyName
,P.SBUArea
,P.ListedOn
,P.Availability
,P.Price
,F.UserID
,F.PID AS FavProjId
FROM Property AS P
LEFT JOIN Favorite AS F
ON (F.PID=P.PID AND F.UserID = #UserId)
Now I wonder if you need that UserId in the WHERE clause of the SQL, or really in the join.
But anyway, here the LINQ-equivalent of exactly that SQL:
System.Int64 __UserId = 12435;
var query = (
from P in Repo.Property
from F in Repo.Favorite
.Where(fav=> fav.PID == P.PID && fav.UserID == __UserId)
.DefaultIfEmpty() // <== makes join left join
select new
{
PID = P.PID
,PropertyName = P.PropertyName
,SBUArea = P.SBUArea
,ListenOn = P.ListedOn
,Availabiity = P.Availability
,Price = P.Price
,UserId = F.UserID
,FavProjId = F.PID
}
);
var data = (query).ToList();
Use anonymous objects in your selection
var result = from t in table1
join x in table2
on t.id equals x.id
select new { id = t.id, col1 = t.col1, col2 = x.col2 }
If you will put the where clause after join you may get null reference exception because DefaultIfEmpty returns default value for non matching rows. You can filter the records before joining itself like this:-
var result=(from p in Properties
join f in Favorites.Where(x => x.UserID == userId)
on p.PID equals f.PID into r
from r1 in r.DefaultIfEmpty()
select new
{
p.PID,
p.PropertyName,
p.SBUArea,
p.ListedOn,
r1.UserId
});
Please note you need to access properties of Favorites using r1.
Update:
As far as I have understood you need all records from Property table and only matching rows from Favorite table. But you have a filter on your Favorite table so the ultimate data source will differ. Let me make my point clear by this example:-
Suppose you have following data in Property table:-
PID PropertyName Availability Price
1 aaa true 20
2 bbb false 10
3 ccc true 50
4 ddd false 80
5 eee true 55
6 fff false 70
and Favorite table like this:-
FID PID UserId
1 4 1001
2 2 1005
3 5 1007
And let's say you want all records for UserId 1005, then the result should contain all the property Id's from 1 till 6 even if UserId 1005 doesn't match for property Id's 4 & 2 right? So the query above is as per this understanding. Check this Fiddle with same example and output.
i would like to have a LINQ statementlike this
in Simple words
i have two tables A and B. A contains fields id,name,amt1,userid. Table B contains id,userid,amt2. I wanted the details of table A in which A.userid=B.userid but B.id!=A.id
Can any one helpmeout. Am a beginner in LINQ
Thanks in advance
Is this what you are trying to do?
TableA.Join(TableB, a => a.userid, b => b.userid, (a, b) => new { A = a, B = b })
.Where(j => j.A.id != j.B.id)
.Select(j => j.A)
Human SQL would be:
select a.*
from tableA a
inner join tableB b on a.userid = b.userid
where a.id != b.id;
please consider this table:
PK_Id Number Year Month Value
-------------------------------------------------------------------------
1 1 2000 5 100000
410 4 2000 6 10000
8888 1 2001 5 100
I Id=8888 and now I want to first select record with Id=8888 and second select previos year of that record*(I mean Id=1)*. How I can do this with linq and one query.
basically we have some queries that first it should find a value from a table (that may be not PK) and find Corresponding records in another tables. How I can do this with linq and one reference to database.
thanks
from a in Record
where a.PK_Id == 8888
from b in Record
where b.Number == a.Number && b.Year == a.Year - 1
select new { Current = a, Previous = b }
or
Record
.Where(a => a.PK_Id == 888)
.SelectMany(a =>
Record
.Where(b => b.Number == a.Number && b.Year == a.Year - 1)
.Select(b => new { Current = a, Previous = b })
If I understand your question right, then you need to filter the data of one table and join two tables.
You can join the tables and filter your data
var query = from c in Table1
join o in Table2 on c.Col1 equals o.Col2
where o.Col3 == "x"
select c;
or you can filter your data from one table and then join the tables (result will be the same)
var query = from c in Table1.Where(item => item.Col3 == "x")
join o in Table2 on c.Col1 equals o.Col2
select c;