I have a one to many relationship in the following tables
Products [ProductId, Name(varchar)]
Keywords [KeywordId, Keyword(varchar)]
KeywordsToProducts[Id, ProductId, KeywordId]
Let's say that search text is "blue pro". I need to search for both keywords using operator 'and'.
If I do the following:
string test="blue pro";
string[]words = test.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
var query = from p in Products
join kp in KeywordsToProducts on p.ProductId equals kp.ProductId
join kw in Keywords on kp.KeywordId equals kw.KeywordId
where (words.All(x=>kw.Keyword.Contains(x)))
then I don't geet anything because field keyword contains only one word.
How can I join the 'Keywrods.Keyword' db field records in order to search using 'and' operator?
If you join each matching KeywordsToProducts to Keywords you can gather them up and compare them:
var query = from p in Products
join kp in KeywordsToProducts on p.ProductId equals kp.ProductId into kpj
let kws = (from kp in kpj join kw in Keywords on kp.KeywordId equals kw.KeywordId select kw.Keyword)
where words.All(w => kws.Any(kw => kw.Contains(w)))
select p;
However, I think it is easier to understand (and possibly more efficient) if you do the KeywordsToProducts to Keywords join separately and first (note that it shows the join table would have been better named KeywordIdsToProductIds):
var kwToProducts = from kp in KeywordsToProducts
join kw in Keywords on kp.KeywordId equals kw.KeywordId
select new { kp.ProductId, kw.Keyword };
var query = from p in Products
join kwp in kwToProducts on p.ProductId equals kwp.ProductId into kwpj
where words.All(w => kwpj.Any(kwp => kwp.Keyword.Contains(w)))
select p;
While I'm not (necessarily) a fan of mentioning it, also note EF navigation properties can hide the join table and make this query easier as well.
It would be something like:
var query = from p in Products
where words.All(w => p.Keywords.Any(k => k.Contains(w)))
select p;
I am assuming you meant to use String.Contains so users can type in parts of keywords and still find matches. If you want to require all of the keyword to be matched, here is the same code:
var query = from p in Products
join kp in KeywordsToProducts on p.ProductId equals kp.ProductId into kpj
let kws = (from kp in kpj join kw in Keywords on kp.KeywordId equals kw.KeywordId select kw.Keyword)
where words.All(w => kws.Contains(w))
select p;
Splitting subjoin:
var kwToProducts = from kp in KeywordsToProducts
join kw in Keywords on kp.KeywordId equals kw.KeywordId
select new { kp.ProductId, kw.Keyword };
var query = from p in Products
join kwp in kwToProducts on p.ProductId equals kwp.ProductId into kwpj
where words.All(w => kwpj.Select(kwp => kwp.Keyword).Contains(w))
select p;
EF Navigation Property:
var query = from p in Products
where words.All(w => p.Keywords.Contains(w))
select p;
Related
SELECT ra.ResidentID, ra.RoomID, r.Number, ra.StartDate, p.FacilityID
FROM(
SELECT ResidentID, MAX(StartDate) AS max_start
FROM RoomAssignments
GROUP BY ResidentID
) m
INNER JOIN RoomAssignments ra
ON ra.ResidentID = m.ResidentID
AND ra.StartDate = m.max_start
INNER JOIN Rooms r
ON r.ID = ra.RoomID
INNER JOIN Person p
ON p.ID = ra.ResidentID
inner join ComplianceStage cs
ON cs.Id = p.ComplianceStageID
ORDER BY ra.EndDate DESC
I'm trying to figure out how to convert this to C# using LINQ. I'm brand new with C# and LINQ and can't get my subquery to fire correctly. Any chance one of you wizards can turn the lights on for me?
Update-----------------
I think I've got the jist of it, but am having trouble querying for the max startdate:
var maxQuery =
from mra in RoomAssignments
group mra by mra.ResidentID
select new { mra.ResidentID, mra.StartDate.Max() };
from ra in RoomAssignments
join r in Rooms on ra.RoomID equals r.ID
join p in Persons on ra.ResidentID equals p.ID
where ra.ResidentID == maxQuery.ResidentID
where ra.StartDate == maxQuery.StartDate
orderby ra.ResidentID, ra.StartDate descending
select new {ra.ResidentID, ra.RoomID, r.Number, ra.StartDate, p.FacilityID}
Following my LINQ to SQL Recipe, the conversion is pretty straight forward if you just follow the SQL. The only tricky part is joining the range variable from the subquery for max start date to a new anonymous object from RoomAssignments that matches the field names.
var maxQuery = from mra in RoomAssignments
group mra by mra.ResidentID into mrag
select new { ResidentID = mrag.Key, MaxStart = mrag.Max(mra => mra.StartDate) };
var ans = from m in maxQuery
join ra in RoomAssignments on m equals new { ra.ResidentID, MaxStart = ra.StartDate }
join r in Rooms on ra.RoomID equals r.ID
join p in Persons on ra.ResidentID equals p.ID
join cs in ComplianceStage on p.ComplianceStageID equals cs.Id
orderby ra.EndDate descending
select new {
ra.ResidentID,
ra.RoomID,
r.Number,
ra.StartDate,
p.FacilityID
};
I am trying to write a linq to get data from many to many tables.
Here are the tables
Products (ID,Name,Description)
Products_Items (ID,ProductID,Description)
ProductsNeeds (ID,Name)
ProductsItems_Needs (ItemID,NeedsID)
This is the t-sql query
select gPro.Name,gProItems.ShortDescription,gProItems.Description,gNeeds.Name
from Products gPro
join Products_Items gProItems on gPro.ID = gProItems.ProductID
join ProductsItems_Needs gProNeeds on gProNeeds.ItemID = gProItems.ID
join ProductsNeeds gNeeds on gNeeds.ID = gProNeeds.NeedsID
where gProItems.ID = 1
this is the linq
var q = from p in objM.Products
join gpItems in objM.Products_Items on p.ID equals gpItems.ProductID
from needs in gpItems.ProductsNeeds
where gpItems.ID == 1
select p;
This query returns (Products) and it has the Produts_Items but it has not the ProductsNeeds.
What modifications should I do in order each Products_items to have the ProductsNeeds?
Thanks
Finally I found the solution.
The change was that instead of returning Products it returns Product_Items.
var q = from pItems in objM.Products_Items
join p in objM.Products on pItems.ID equals p.ID into joinedProducts
from p in joinedProducts.DefaultIfEmpty()
from needs in pItems.ProductsNeeds
where pItems.ID == 1
select pItems;
I have three tables. Two of them join equally but one will need to join with a left. I'm finding a lot of code to do this in linq but between two tables only.
Here is the SQL code that I'm trying to re-code within LINQ.
SELECT PRSN.NAME
,CO.NAME
,PROD.NAME
FROM PERSON PRSN
INNER JOIN COMPANY CO ON PRSN.PERSON_ID = CO.PERSON_ID
LEFT OUTER JOIN PRODUCT PROD ON PROD.PERSON_ID = PROD.PERSON_ID;
Here is a snippet of LINQ code that I'm using as a base. I'm just not able to piece together the third table (product in my sample SQL) via LINQ and with a left outer join. The sample is between two tables. Thanks for any tips.
var leftOuterJoinQuery =
from category in categories
join prod in products on category.ID equals prod.CategoryID into prodGroup
from item in prodGroup.DefaultIfEmpty(new Product{Name = String.Empty, CategoryID = 0})
select new { CatName = category.Name, ProdName = item.Name };
Michael
How about this:
var loj = (from prsn in db.People
join co in db.Companies on prsn.Person_ID equals co.Person_ID
join prod in db.Products on prsn.Person_ID equals prod.Person_ID into prods
from x in prods.DefaultIfEmpty()
select new { Person = prsn.NAME, Company = co.NAME, Product = x.NAME })
EDIT: if you want to do a left outer join on all tables, you can do it like this:
var loj = (from prsn in db.People
join co in db.Companies on prsn.Person_ID equals co.Person_ID into comps
from y in comps.DefaultIfEmpty()
join prod in db.Products on prsn.Person_ID equals prod.Person_ID into prods
from x in prods.DefaultIfEmpty()
select new { Person = prsn.NAME, Company = y.NAME, Product = x.NAME })
Taken from another Stackoverflow thread somewhere, there's a more legible way to do this:
var loj = (from prsn in db.People
from co in db.Companies.Where(co => co.Person_ID == prsn.Person_ID).DefaultIfEmpty()
from prod in db.Products.Where(prod => prod.Person_ID == prsn.Person_ID).DefaultIfEmpty()
select new { Person = prsn.NAME, Company = co.NAME, Product = prod.NAME })
This uses a mix of linq query syntax and lambda syntax to what (I believe is) the best result. There's no copious re-aliasing of identifiers, and it's the most concise way to do this that I've seen.
I have this simple sql query:
select c.LastName, Sum(b.Debit)- Sum(b.Credit) as OpenBalance from Balance as b
inner join Job as j on (b.Job = j.ID)
inner join Client as c on (j.Client = c.ID)
Group By c.LastName
and I am trying to convert it to work in linq like this:
from b in Balance
join j in Job on b.Job equals j.ID
join c in Client on j.Client equals c.ID
group b by new { c.LastName } into g
select new {
Name = c.Lastname,
OpenBalance = g.Sum(t1 => t1.Credit)
}
but when I try to run it in LINQPad I get the following message:
The name 'c' does not exist in the
current context
and it highlights c.Lastname in select new statement.
Any help on this will be greatly appreciated.
Thank you.
Well, you've grouped b by c.LastName. So after the grouping operation, you're dealing with g which is a grouping with the element type being the type of b, and the key type being the type of c.LastName. It could well be that all you need is:
select new {
Name = g.Key,
OpenBalance = g.Sum(t1 => t1.Credit)
}
... but if you need to get at any other aspects of c, you'll need to change your grouping expression.
Using LinqToSql, I need to return a single (L) for the most recent modDate in a join table (CL).
Tables:
L (Lid, meta1, meta2, ...)
CL (Cid, Lid, ModDate)
Here is sql that produces the expected result
SELECT l.*
FROM L l
INNER JOIN (
SELECT TOP 1 cl.Lid, MAX(cl.ModDate) as ModDate
FROM CL cl
INNER JOIN L l ON cl.Lid = l.Lid AND l.meta1 = 5
GROUP BY cl.Lid
ORDER BY MAX(cl.ModDate) DESC
) As m ON l.Lid = m.Lid
Simple enough. The subquery projects us to the ids. The query fetches those records with matching ids.
var subquery = db.L
.Where(L => L.meta1 = 5)
.SelectMany(L => L.CLs)
.GroupBy(CL => CL.Lid)
.OrderByDescending(g => g.Max(CL => CL.ModDate))
.Select(g => g.Key)
.Take(1)
var query = db.L
.Where(L => subquery.Any(id => L.Lid == id))
Reflecting on this further, you can get away from the subquery:
var query = db.L
.Where(L => L.meta1 = 5)
.SelectMany(L => L.CLs)
.GroupBy(CL => CL.Lid)
.OrderByDescending(g => g.Max(CL => CL.ModDate))
.Select(g => g.First().L);
As your provided query, I can interpret into this Linq.
var query = from l in Context.L
join m in (from cl in Context.CL
join l in Context.L on cl.Lid equals l.Lid
where l.meta1 == 5
group new { l.Lid, cl.ModDate } by cl.Lid into grp
select new { Lid = grp.Key, ModDate = grp.Max(g => g.ModDate) } into grp
order by grp.ModDate descending
select grp).Take(1) on l.Lid equals m.Lid
select l;
My SQL-fu isn't fabulous and it's before my first coffee, so I assume "l" in the outer query ends up being a completely different "l" to the one in the subquery?
I think this will do it, but you'll have to try to be sure :) It'll be well worth checking what the generated SQL looks like. If you didn't mind it executing as two queries, of course, it would be somewhat simpler.
// Can't do the "Take(1)" here or it will be executed separately
var subquery = from cl in context.CL
join l in context.L on cl.Lid = l.Lid
where l.meta1 = 5 // could put this in join clause
group cl.ModDate by cl.lid into grouped
order by grouped.Max() descending
select grouped.Key;
// But can take the first result of the join
// This may be simpler using dot notation instead of a query expression
var query = (from l in context.L
join lid in subquery
select l).Take(1);
(EDIT: I wasn't taking the max ModDate before. Doh. Also simplified grouping by using the ID as the key (which it was already) so we only need the ModDate as the group values.)