I'm trying to learn linq..I have the following linq query..
var abc = consumers.Where(w => plays.Any(x => x.consumerid == w.consumerid));
I would appreciate if someone could help me with its corresponding sql query.
consumers have just two fields.. consumerid and period both string.
plays also have two fields.. consumerid and playid both string.
Based on answer here.. I tried abc.ToString() but that did not help..
Simplified query:
SELECT *
FROM consumers x
WHERE EXISTS
(
SELECT *
FROM plays w
WHERE x.consumerid = w.consumerid
)
Try this:
select * from consumers c left join palys p on c.consumerid = p.consumerid
Related
I am trying to compare two tables (i.e values, count, etc..) in linq to sql but I am not getting the way to achieve it. I tried the following,
Table1.Any(i => i.itemNo == Table2.itemNo)
It gives error. Could you please help me?
Thanks in Advance.
how about
var isDifferent =
Table1.Zip(Table2, (j, k) => j.itemNo == k.itemMo).Any(m => !m);
EDIT
if Linq-To-Sql does not support Zip.
var one = Table1.ToList();
var two = Table2.ToList();
var isDifferent =
one.Zip(two, (j, k) => j.itemNo == k.itemMo).Any(m => !m);
if the tables are vary large this could cause performance problems. In that case you will need a much more sophisticated solution, if so, please ask.
EDIT2
If the tables are very large you don't want to get all the data from the server and hold it memory. Additionaly, Linq and SQL server do not garauntee the order of the rows unless you specify an order in the query. This becomes espcially relavent for large result sets returned by a multi processor server where the effects of parallelism are likely to come into play.
I suggest that Linq-to-Sql doesen't really cater well for your scenario so you will have to help it out using ExecuteQuery somthing like this.
string zipQuery =
#"SELECT TOP 1
1
FROM
[Table1] [one]
WHERE
NOT EXISTS (
SELECT * FROM [Table2] [two] WHERE [two].[itemNo] = [one].[itemNo]
)
UNION ALL
SELECT
1
FROM
[Table2] [two]
WHERE
NOT EXISTS (
SELECT * FROM [Table1] [one] WHERE [one].[itemNo] = [two].[itemNo]
)
UNION ALL
SELECT 0";
var isDifferent = context.ExecuteQuery<int>(zipQuery).Single() == 1;
This will do the select on the server without returning lots of data to the client but, I think you will agree is much more complicated.
EDIT3
Okay, the zip approach should be fine for 1000 rows. I've read your comment and I suggest changing the code accordingly.
var one = Table1.ToList();
var two = Table2.ToList();
var isDifferent =
one.Count != two.Count ||
one.Zip(two, (o, t) => o.itemNo == k.itemNo).Any(m => !m);
You should probably consider putting an order by on the list retrievers, like this.
var one = Table1.OrderBy(o => o.itemNo).ToList();
Strictly, the results of a Linq-to-Sql come back in any order unless an order is specified.
I'm having a bit trouble with a query in Linq to Entities which I hope someone can shed a light on :-) What I'm trying to do is to create a query that joins three tables.
So far it works, but since the last table I'm trying to join is empty, the result of the query doesn't contain any records. When I remove the last join, it gives me the right results.
My query looks like this:
var query = from p in db.QuizParticipants
join points in db.ParticipantPoints on p.id
equals points.participantId into participantsGroup
from po in participantsGroup
join winners in db.Winners on p.id
equals winners.participantId into winnersGroup
from w in winnersGroup
where p.hasAttended == 1 && p.weeknumber == weeknumber
select new
{
ParticipantId = p.id,
HasAttended = p.hasAttended,
Weeknumber = p.weeknumber,
UmbracoMemberId = p.umbMemberId,
Points = po.points,
HasWonFirstPrize = w.hasWonFirstPrize,
HasWonVoucher = w.hasWonVoucher
};
What I would like is to get some records even if the Winners table is empty or there is no match in it.
Any help/hint on this is greatly appreciated! :-)
Thanks a lot in advance.
/ Bo
If you set these up as related entities instead of doing joins, I think it will be easier to do what you're trying to do.
var query = from p in db.QuizParticipants
where p.hasAttended == 1 && p.weeknumber == weeknumber
select new
{
ParticipantId = p.id,
HasAttended = p.hasAttended,
Weeknumber = p.weeknumber,
UmbracoMemberId = p.umbMemberId,
Points = p.ParticipantPoints.Sum(pts => pts.points),
HasWonFirstPrize = p.Winners.Any(w => w.hasWonFirstPrize),
HasWonVoucher = p.Winners.Any(w => w.hasWonVoucher)
};
This is assuming hasWonFirstPrize and hasWonVoucher are boolean fields, but you can use any aggregate function to get the results you need, such as p.Winners.Any(w => w.hasWonFirstPrize == 1)
I don't use query syntax a lot but I believe you need to change from w in winnersGroup to from w in winnersGroup.DefaultIfEmpty()
Can anybody tell me how I would get the records in the first statement that are not in the second statement (see below)?
from or in TblOrganisations
where or.OrgType == 2
select or.PkOrgID
Second query:
from o in TblOrganisations
join m in LuMetricSites
on o.PkOrgID equals m.FkSiteID
orderby m.SiteOrder
select o.PkOrgID
If you only need the IDs then Except should do the trick:
var inFirstButNotInSecond = first.Except(second);
Note that Except treats the two sequences as sets. This means that any duplicate elements in first won't be included in the results. I suspect that this won't be a problem since the name PkOrgID suggests a unique ID of some kind.
(See the documentation for Enumerable.Except and Queryable.Except for more info.)
Do you need the whole records, or just the IDs? The IDs are easy...
var ids = firstQuery.Except(secondQuery);
EDIT: Okay, if you can't do that, you'll need something like:
var secondQuery = ...; // As you've already got it
var query = from or in TblOrganisations
where or.OrgType == 2
where !secondQuery.Contains(or.PkOrgID)
select ...;
Check the SQL it produces, but I think it should do the right thing. Note that there's no point in performing any ordering in the second query - or even the join against TblOrganisations. In other words, you could use:
var query = from or in TblOrganisations
where or.OrgType == 2
where !LuMetricSites.Select(m => m.FkSiteID).Contains(or.PkOrgID)
select ...;
Use Except:
var filtered = first.Except(second);
I have the following query to start with:
var query = from p in db.Products
from pc in p.NpProductCategories
where pc.CategoryId == categoryId
select p;
I'm applying some more filtering on it and in the end I want to sort the results:
if (orderBy == ProductSortingEnum.Name)
query = query.OrderBy(x => x.Name);
else
query = query.OrderBy(............);
My big problem (coming from not knowing linq too good) is the ELSE here. How can I sort results by a column that is not in the current result set? I would like to somehow link to another linq query in the orderby. The sorting I'm trying to achive is to link to NpProductVariants query using the ProductId to match between NpProductVariant and Products
and sort by the Price of the NpProductVariant
Assuming you have the relationship set up in the dbml...
For one to one (and many to one):
query = query.OrderBy(p => p.NpProductVariant.Price);
For one to many:
query = query.OrderBy(p => p.NpProductVariants.Select(v => v.Price).Max());
Also:
var query =
from p in db.Products
where p.NpProductCategories.Any(pc => pc.CategoryId == categoryId)
select p;
I think you can hook your Join to your query as long as it is returning the same thing. So maybe something like (I'm not 100 % sure since I haven't tried it):
query = from i1 in query
join i2 in query2 on i1.PropertyToJoin equals i2.PropertyToJoin
orderby i1.OrderProp1, i2.OrderProp2
select i1;
But I think it might be a good idea to check the generated sql so it is still effective.
I had tried to join two table conditionally but it is giving me syntax error. I tried to find solution in the net but i cannot find how to do conditional join with condition. The only other alternative is to get the value first from one table and make a query again.
I just want to confirm if there is any other way to do conditional join with linq.
Here is my code, I am trying to find all position that is equal or lower than me. Basically I want to get my peers and subordinates.
from e in entity.M_Employee
join p in entity.M_Position on e.PostionId >= p.PositionId
select p;
You can't do that with a LINQ joins - LINQ only supports equijoins. However, you can do this:
var query = from e in entity.M_Employee
from p in entity.M_Position
where e.PostionId >= p.PositionId
select p;
Or a slightly alternative but equivalent approach:
var query = entity.M_Employee
.SelectMany(e => entity.M_Position
.Where(p => e.PostionId >= p.PositionId));
Following:
from e in entity.M_Employee
from p in entity.M_Position.Where(p => e.PostionId >= p.PositionId)
select p;
will produce exactly the same SQL you are after (INNER JOIN Position P ON E..PostionId >= P.PositionId).
var currentDetails = from c in customers
group c by new { c.Name, c.Authed } into g
where g.Key.Authed == "True"
select g.OrderByDescending(t => t.EffectiveDate).First();
var currentAndUnauthorised = (from c in customers
join cd in currentDetails
on c.Name equals cd.Name
where c.EffectiveDate >= cd.EffectiveDate
select c).OrderBy(o => o.CoverId).ThenBy(o => o.EffectiveDate);
If you have a table of historic detail changes including authorisation status and effective date. The first query finds each customers current details and the second query adds all subsequent unauthorised detail changes in the table.
Hope this is helpful as it took me some time and help to get too.