I am using LINQ to write a query - one query shows all active customers , and another shows all active as well as inactive customers.
if(showall)
{
var prod = Dataclass.Customers.Where(multiple factors ) (all inactive + active)
}
else
{
var prod = Dataclass.Customers.Where(multiple factors & active=true) (only active)
}
Can I do this using only one query? The issue is that, multiple factors are repeated in both the queries
thanks
var customers = Dataclass.Customers.Where(multiple factors);
var activeCust = customers.Where(x => x.active);
I really don't understand the question either. I wouldn't want to make this a one-liner because it would make the code unreadable
I'm assuming you are trying to minimze the number of roundtrips?
If "multiple factors" is the same, you can just filter for active users after your first query:
var onlyActive = prod.Where(p => p.active == true);
Wouldn't you just use your first query to return all customers?? If not you'd be returning the active users twice.
Options I'd consider
Bring all customers once, order by 'status' column so you can easily split them into two sets
Focus on minimizing DB roundtrips. Whatever you do in the front end costs an order of magnitude less than going to the DB.
Revise user requirements. For ex. consider paging on results - it's unlikely that end user will need all customers at once.
Related
int mappedCount = (from product in products
from productMapping in DbContext.ProductCategoryMappings
.Where(x => product.TenantId == x.TenantId.ToString() &&
x.ProductId.ToString().ToUpper() == product.ProductGuid.ToUpper())
join tenantCustMapping in DbContext.TenantCustCategories
on productMapping.Value equals tenantCustMapping.Id
select 1).ToList().Sum();
I need to increase the performance.
When mapping product two tables each item having multiple product
If you want to increase performance, you'd need to know the volumes of data that are getting sent around. How many "products" are in your variable.
It may be quicker to update your products list to contain integers / guids and send that to your database rather than send strings that the database has to run ToUpper() on before comparing them.
something like:
var convertedList = products.Select( new {TenantId = int.parse(product.TenantId), productId = Guid.Parse(x.ProductId)}
Then sending that to your Db, and comparing them directly
I think changing "Select 1).ToList().Sum()" to ".Count()" will improve performance. Even if not, it'll help readability.
I have a table with 5 categories and units displayed into 2 types, Actual and budget.
I want to filter this table. Only when 2 or more values are selected in the slicer. Something like this.
I though of adding a measure, but dont know how to work the if statement exactly.
Measure = IF(COUNTROWS(ALLSELECTED(Report[Shipment Group])) = 1, "Something which would not filter the units", SELECTEDVALUE(Report[Units], SUM(Report[Units])))
Not sure if this is correct approach.Would like to know if any other approach is possible. Any help would be helpful. Thank you in advance.
This is a bit of an odd request, but I think I have something that works.
First, you need to create a separate table for your slicer values (or else you can't control filtering how you want). You can hit the new table button and define it as follows:
Groups = VALUES(Report[Shipment Group])
Set your slicer to use Groups[Shipment Group] instead of Report[Shipment Group].
Define your new measure as follows:
Measure = IF(COUNTROWS(ALLSELECTED(Groups[Shipment Group])) = 1,
SUM(Report[Units]),
SUMX(FILTER(Report,
Report[Shipment Group] IN VALUES(Groups[Shipment Group])),
Report[Units]))
or equivalently
Measure = IF(COUNTROWS(ALLSELECTED(Groups[Shipment Group])) = 1,
SUM(Report[Units]),
CALCULATE(SUM(Report[Units]),
FILTER(Report,
Report[Shipment Group] IN VALUES(Groups[Shipment Group]))))
Note: Double check that Power BI has not automatically created a relationship between the Groups and Report tables. You don't want that.
I'm attempting to make a linq where contains query quicker.
The data set contains 256,999 clients. The Ids is just a simple list of GUID'S and this would could only contain 3 records.
The below query can take up to a min to return the 3 records. This is because the logic will go through the 256,999 record to see if any of the 256,999 records are within the List of 3 records.
returnItems = context.ExecuteQuery<DataClass.SelectClientsGridView>(sql).Where(x => ids.Contains(x.ClientId)).ToList();
I would like to and get the query to check if the three records are within the pot of 256,999. So in a way this should be much quicker.
I don't want to do a loop as the 3 records could be far more (thousands). The more loops the more hits to the db.
I don't want to grap all the db records (256,999) and then do the query as it would take nearly the same amount of time.
If I grap just the Ids for all the 256,999 from the DB it would take a second. This is where the Ids come from. (A filtered, small and simple list)
Any Ideas?
Thanks
You've said "I don't want to grab all the db records (256,999) and then do the query as it would take nearly the same amount of time," but also "If I grab just the Ids for all the 256,999 from the DB it would take a second." So does this really take "just as long"?
returnItems = context.ExecuteQuery<DataClass.SelectClientsGridView>(sql).Select(x => x.ClientId).ToList().Where(x => ids.Contains(x)).ToList();
Unfortunately, even if this is fast, it's not an answer, as you'll still need effectively the original query to actually extract the full records for the Ids matched :-(
So, adding an index is likely your best option.
The reason the Id query is quicker is due to one field being returned and its only a single table query.
The main query contains sub queries (below). So I get the Ids from a quick and easy query, then use the Ids to get the more details information.
SELECT Clients.Id as ClientId, Clients.ClientRef as ClientRef, Clients.Title + ' ' + Clients.Forename + ' ' + Clients.Surname as FullName,
[Address1] ,[Address2],[Address3],[Town],[County],[Postcode],
Clients.Consent AS Consent,
CONVERT(nvarchar(10), Clients.Dob, 103) as FormatedDOB,
CASE WHEN Clients.IsMale = 1 THEN 'Male' WHEN Clients.IsMale = 0 THEN 'Female' END As Gender,
Convert(nvarchar(10), Max(Assessments.TestDate),103) as LastVisit, ";
CASE WHEN Max(Convert(integer,Assessments.Submitted)) = 1 Then 'true' ELSE 'false' END AS Submitted,
CASE WHEN Max(Convert(integer,Assessments.GPSubmit)) = 1 Then 'true' ELSE 'false' END AS GPSubmit,
CASE WHEN Max(Convert(integer,Assessments.QualForPay)) = 1 Then 'true' ELSE 'false' END AS QualForPay,
Clients.UserIds AS LinkedUsers
FROM Clients
Left JOIN Assessments ON Clients.Id = Assessments.ClientId
Left JOIN Layouts ON Layouts.Id = Assessments.LayoutId
GROUP BY Clients.Id, Clients.ClientRef, Clients.Title, Clients.Forename, Clients.Surname, [Address1] ,[Address2],[Address3],[Town],[County],[Postcode],Clients.Consent, Clients.Dob, Clients.IsMale,Clients.UserIds";//,Layouts.LayoutName, Layouts.SubmissionProcess
ORDER BY ClientRef
I was hoping there was an easier way to do the Contain element. As the pool of Ids would be smaller than the main pool.
A way I've speeded it up for now is. I've done a Stinrg.Join to the list of Ids and added them as a WHERE within the main SQL. This has reduced the time down to a seconds or so now.
I've read through the Crossfilter API docs several times but can't see how to do the following.
Suppose I have set up
crossfilter(event);
and a dimension foo:
var foo = event.dimension(function(d) { return d.foo; }),
foos = foo.group(function(d) { return Math.floor(d) ; });
Then, before any filters are applied, event.size() will give me the number of records in the event, and foos.size() will give me the number of distinct records in the foo dimension
Great! Now I apply some filters by sliding brushes around. event.groupAll().value() now gives me the current number of records in event that are selected. Great again.
Now how do I get the current number of distinct records in the foo dimension? I've tried many different combinations of the API primitives, but none seem to work.
Any ideas?
This should do the trick
var n = foo.top(Number.POSITIVE_INFINITY).length;
I do not have enough reputation to comment the solution proposed by Reno.
This should do the trick
var n = foo.top(Number.POSITIVE_INFINITY).length;
The problem of this solution is that is not efficient, because top function is ordering the data.
I have the same problem that you and I have a counter in the filter to know how many entries have the dimension.
I have a database with customers orders.
I want to use Linq (to EF) to query the db to bring back the last(most recent) 3,4...n orders for every customer.
Note:
Customer 1 may have just made 12 orders in the last hr; but customer 2 may not have made any since last week.
I cant for the life of me work out how to write query in linq (lambda expressions) to get the data set back.
Any good ideas?
Edit:
Customers and orders is a simplification. The table I am querying is actually a record of outbound messages to various web services. It just seemed easer to describe as customers and orders. The relationship is the same.
I am building a task that checks the last n messages for each web service to see if there were any failures. We are wanting a semi real time Health status of the webservices.
#CoreySunwold
My table Looks a bit like this:
MessageID, WebserviceID, SentTime, Status, Message, Error,
Or from a customer/order context if it makes it easer:
OrderID, CustomerID, StatusChangedDate, Status, WidgetName, Comments
Edit 2:
I eventually worked out something
(Hat tip to #StephenChung who basically came up with the exact same, but in classic linq)
var q = myTable.Where(d => d.EndTime > DateTime.Now.AddDays(-1))
.GroupBy(g => g.ConfigID)
.Select(g =>new
{
ConfigID = g.Key,
Data = g.OrderByDescending(d => d.EndTime)
.Take(3).Select(s => new
{
s.Status,
s.SentTime
})
}).ToList();
It does take a while to execute. So I am not sure if this is the most efficient expression.
This should give the last 3 orders of each customer (if having orders at all):
from o in db.Orders
group o by o.CustomerID into g
select new {
CustomerID=g.Key,
LastOrders=g.OrderByDescending(o => o.TimeEntered).Take(3).ToList()
}
However, I suspect this will force the database to return the entire Orders table before picking out the last 3 for each customer. Check the SQL generated.
If you need to optimize, you'll have to manually construct a SQL to only return up to the last 3, then make it into a view.
You can use SelectMany for this purpose:
customers.SelectMany(x=>x.orders.OrderByDescending(y=>y.Date).Take(n)).ToList();
How about this? I know it'll work with regular collections but don't know about EF.
yourCollection.OrderByDescending(item=>item.Date).Take(n);
var ordersByCustomer =
db.Customers.Select(c=>c.Orders.OrderByDescending(o=>o.OrderID).Take(n));
This will return the orders grouped by customer.
var orders = orders.Where(x => x.CustomerID == 1).OrderByDescending(x=>x.Date).Take(4);
This will take last 4 orders. Specific query depends on your table / entity structure.
Btw: You can take x as a order. So you can read it like: Get orders where order.CustomerID is equal to 1, OrderThem by order.Date and take first 4 'rows'.
Somebody might correct me here, but i think doing this is linq with a single query is probably very difficult if not impossible. I would use a store procedure and something like this
select
*
,RANK() OVER (PARTITION BY c.id ORDER BY o.order_time DESC) AS 'RANK'
from
customers c
inner join
order o
on
o.cust_id = c.id
where
RANK < 10 -- this is "n"
I've not used this syntax for a while so it might not be quite right, but if i understand the question then i think this is the best approach.