I want to write an query with group by and count clause in Entity framework. like employees and managers and display all employees based on manager
any code samples
Thanks
var employeesByManager = db.Employees.
GroupBy(emp => emp.Manager.EmployeeName, emp => emp).
ToList();
var employeeCountsByManager = db.Employees.
Select(emp => new { ManagerName = emp.EmployeeName, EmployeeCount = emp.Employees.Count() }).
Where(a => a.EmployeeCount > 0).
ToList();
You can, of course, get the employees grouped by manager in a similar manner as counts. The GroupBy method is just a simpler way to do this.
Related
I'm currently working on a database with several one-to-many and many-to-many relationships and I am struggling getting ormlite to work nicely.
I have a one-to-many relationship like so:
var q2 = Db.From<GardnerRecord>()
.LeftJoin<GardnerRecord, GardnerEBookRecord>((x, y) => x.EanNumber == y.PhysicalEditionEan)
I need to return a collection of ProductDto that has a nested list of GardnerEBookRecord.
Using the SelectMult() technique it doesn't work because the pagination breaks as I am condensing the left joined results to a smaller collection so the page size and offsets are all wrong (This method: How to return nested objects of many-to-many relationship with autoquery)
To get the paging right I need to be able to do something like:
select r.*, count(e) as ebook_count, array_agg(e.*)
from gardner_record r
left join gardner_e_book_record e
on r.ean_number = e.physical_edition_ean
group by r.id
There are no examples of this in the docs and I have been struggling to figure it out. I can't see anything that would function like array_agg in the Sql object of OrmLite.
I have tried variations of:
var q2 = Db.From<GardnerRecord>()
.LeftJoin<GardnerRecord, GardnerEBookRecord>((x, y) => x.EanNumber == y.PhysicalEditionEan)
.GroupBy(x => x.Id).Limit(100)
.Select<GardnerRecord, GardnerEBookRecord>((x, y) => new { x, EbookCount = Sql.Count(y), y }) //how to aggregate y?
var res2 = Db.SelectMulti<GardnerRecord, GardnerEBookRecord>(q2);
and
var q2 = Db.From<GardnerRecord>()
.LeftJoin<GardnerRecord, GardnerEBookRecord>((x, y) => x.EanNumber == y.PhysicalEditionEan)
.GroupBy(x => x.Id).Limit(100)
.Select<GardnerRecord, List<GardnerEBookRecord>>((x, y) => new { x, y });
var res = Db.SqlList<object>(q2);
But I can't work out how to aggregate the GardnerEBookRecord to a list and keep the paging and offset correct.
Is this possible? Any workaround?
edit:
I made project you can run to see issue:
https://github.com/GuerrillaCoder/OneToManyIssue
Database added as a docker you can run docker-compose up. Hopefully this shows what I am trying to do
Npgsql doesn't support reading an unknown array or records column type, e.g array_agg(e.*) which fails with:
Unhandled Exception: System.NotSupportedException: The field 'ebooks' has a type currently unknown to Npgsql (OID 347129).
But it does support reading an array of integers with array_agg(e.id) which you can query instead:
var q = #"select b.*, array_agg(e.id) ids from book b
left join e_book e on e.physical_book_ean = b.ean_number
group by b.id";
var results = db.SqlList<Dictionary<string,object>>(q);
This will return a Dictionary Dynamic Result Set which you'll need to combine into a distinct id collection to query all ebooks referenced, e.g:
//Select All referenced EBooks in a single query
var allIds = new HashSet<int>();
results.Each(x => (x["ids"] as int[])?.Each(id => allIds.Add(id)));
var ebooks = db.SelectByIds<EBook>(allIds);
Then you can create a dictionary mapping of id => Ebook and use it to populate a collection of ebooks entities using the ids for each row:
var ebooksMap = ebooks.ToDictionary(x => x.Id);
results.Each(x => x[nameof(ProductDto.Ebooks)] = (x["ids"] as int[])?
.Where(id => id != 0).Map(id => ebooksMap[id]) );
You can then use ServiceStack AutoMapping Utils to convert each Object Dictionary into your Product DTO:
var dtos = results.Map(x => x.ConvertTo<ProductDto>());
I am basically trying to run a query that gives me all the Users that have purchased a product with a particular SKU. Essentially this SQL here:
SELECT u.FirstName, u.LastName, u.Email
FROM COM_OrderItem oi INNER JOIN COM_Order o ON oi.OrderItemOrderID = o.OrderID
INNER JOIN COM_Customer c ON o.OrderCustomerID = c.CustomerID
INNER JOIN CMS_User u ON c.CustomerUserID = u.UserID
WHERE oi.OrderItemSKUID = 1013
I was trying to use the ObjectQuery API to try and achieve this but have no idea how to do this. The documentation here does not cover the specific type of scenario I am looking for. I came up with this just to try and see if it works but I don't get the three columns I am after in the result:
var test = OrderItemInfoProvider
.GetOrderItems()
.Source(orderItems => orderItems.Join<OrderInfo>("OrderItemOrderID", "OrderID"))
.Source(orders => orders.Join<CustomerInfo>("OrderCustomerID", "CustomerID"))
.Source(customers => customers.Join<UserInfo>("CustomerUserID", "UserID"))
.WhereEquals("OrderItemSKUID", 1013).Columns("FirstName", "LastName", "Email").Result;
I know this is definitely wrong and I would like to know the right way to achieve this. Perhaps using ObjectQuery is not the right approach here or maybe I can somehow just use raw SQL. I simply don't know enough about Kentico to understand the best approach here.
Actually, the ObjectQuery you created is correct. I tested it and it is providing the correct results. Are you sure that there are indeed orders in the system, which contain a product with SKUID 1013 (you can check that in the COM_OrderItem database table)?
Also, how are you accessing the results? Iterating through the results should look like this:
foreach (DataRow row in test.Tables[0].Rows)
{
string firstName = ValidationHelper.GetString(row["FirstName"], "");
string lastName = ValidationHelper.GetString(row["LastName"], "");
string email = ValidationHelper.GetString(row["Email"], "");
}
It may be I'm still thinking in the Linq2Sql mode, but I'm having a hard time translating this to OrmLite.
I have a customers table and a loyalty card table.
I want to get a list of customers and for each customer, have a list of express cards.
My strategy is to select customers, join to loyalty cards, group by whole customer table, and then map the cards to a single property on customer as a list.
Things are not named by convention, so I don't think I can take advantage of the implicit joins.
Thanks in advance for any help.
Here is the code I have now that doesn't work:
query = query.Join<Customer, LoyaltyCard>((c, lc) => c.CustomerId == lc.CustomerId)
.GroupBy(x => x).Select((c) => new { c, Cards = ?? What goes here? });
Edit: I thought maybe this method:
var q = db.From<Customer>().Take(1);
q = q.Join<Customer, LoyaltyCard>().Select();
var customer = db.SelectMulti<Customer,LoyaltyCard>(q);
But this is giving me an ArgumentNullException on parameter "key."
It's not clear from the description or your example code what you're after, but you can fix your SelectMulti Query with:
var q = db.From<Customer>()
.Join<Customer, LoyaltyCard>();
var results = db.SelectMulti<Customer,LoyaltyCard>(q);
foreach (var tuple in results)
{
Customer customer = tuple.Item1;
LoyaltyCard custCard = tuple.Item2;
}
I'm trying to create a repository of data that I can use for testing purposes for an emerging car production and design company.
Beginning Automapper Question:
In this project, I have 2 classes that share the same properties for the most part. I don't need the Id, so I am ignoring that.
My existing code looks like this:
Mapper.CreateMap<RaceCar, ProductionCar>()
.Ignore(d => d.fId) //ignore the ID
.ForMember(d=> d.ShowRoomName,
o=> o.MapFrom(s => s.FactoryName) //different property names but same thing really
//combine into my new test car
var testCarObject = Mapper.Map<RaceCar, ProductionCar>()
My main requirements are:
1) I need to create 100 of these test car objects
2) and that for every ProductionCar I use, it needs to have a corresponding RaceCar which are matched up by the name(ShowRoomName & FactoryName)
So is there a way of sticking this in some type of loop or array so that I can create the needed 100?
Also, is there a way to ensure that each new test car has the combined FactoryCar and RaceCar?
Thanks!
Use AutoMapper with AutoFixture:
var fixture = new Fixture();
var items = Enumerable.Range(1, 100)
.Select(i => fixture.Create<RaceCar>())
.Select(car => new { RaceCar = car, ProductionCar = Mapper.Map<RaceCar, ProductionCar>(car))
.ToList();
items.Profit()
I have a products model with 2 many to many relationships defined.
protected $_has_many = array
(
'foodcats' => array('model' => 'foodcat', 'through' => 'products_foodcats'),
'foodgroups' => array('model' => 'foodgroup', 'through' => 'products_foodgroups')
)
I need a query where I find products with a given foodcat id and a given foodgroup name.
I know I can do the following to get all products with a given foodcat id
$foodcat = ORM::factory('foodcat',$foodCatId);
$products = $foodcat->products->find_all();
But how do I query for products in that foodcat that also are in the foodgroup 'Entrees'?
Thanks!
Simply; you don't. What you need is INNER JOIN, like;
ORM::factory('product')
->join('foodcats','INNER')
->on('foodcats.id','=',$foodcats_id)
->join('foodgroups','INNER')
->on('foodgroups.name','=',$foodgroups_name)
->find_all();
in Kohana 3.1 without using DB::expr, will give unknown column error.
ORM::factory('product')
->join('foodcats','INNER')
->on('foodcats.id','=', DB::expr($foodcats_id))
->join('foodgroups','INNER')
->on('foodgroups.name','=', DB::expr($foodgroups_name))
->find_all();