I am using linqpad. I have an ODATA connected. The entities are listed in left pane with relationships. There are two entities called Products and Customers. I have to get all the product id starting with pid and names of all customers startin with b. There is a relationship between both. Product is a child of customer. How do I do? I am trying since two days but unable to figure it out. Anyone could help?
this is the base code. i dont no what to do further.
from p in products
where p.ProductId.StartsWith("Pid")
from c in customers
where c.Name.StartsWith("B")
select new
{
p.Pid,
c.Name
};
Can you please specify how you want the relation between the two entities to affect the result of the query? Do you expect the above to only returns products (with ID starting with a given value) and then only the customers for those products which name starts with a certain value?
Such a query is not expressible in OData unfortunately. You could request all products which ID starts with a specific value, and all the related customers. And then filter the customers on the client.
For example this will get you all the products which ID starts with a certain value and all their customers:
from p in products
where p.ProductId.StartsWith("Pid")
select new Product
{
ProductId = p.ProductId,
Customers = p.Customers
};
Related
I am running into an issue with writing an SQL query with Google Big Query. Basically looking to transfer the top products, per country, per category which are also in stock into a table.
So far I have pulled in the top products, per country, per category but the issue is with getting the 'in-stock' part added to the table. I can't find any similar keys in the schema to match them up.
Ideally the table would include:
Rank, Product Title, Country, Category, In-Stock
I would really appreciate any help on this! Thanks.
I have tried to add in a separate table that includes the 'availability' key for each product but I could not match it
You have your top_products table to check the rank that you can join to the product_inventory using the rank_id.
This join will retrieve the product_id and join that key to the products table.
After that, you get the availability information of the product and then you have all the information you require.
My task: "Compile an SQL query that outputs a specific store (enter parameter window) the age of the youngest buyer"
I´ve tried some things, but because i´m new to SQL and i have no idea what i´m doing non of them seem to work.
I´d really appreciate, if someone would help me.
Thanks!
First you need to know the fields to SELECT (or return) and the table FROM which you are querying (asking) data; let's say you have the following tables: tblStores (containing a list of stores and related info), tblCustomers (containing customers and related info, e.g. ages, names, phone numbers, etc.), and tblPurchases (containing all the purchases at all stores by all customers and related info). You want the minimum age of a customer making a purchase at a specfic store, so you could use a MIN aggregating function. You would want to join (or relate) the tables based on customers and purchases. See my INNER JOINs in the example below. Then you filter the result by the user-inputted store name (inputStoreName) using WHERE; since the inputStoreName is undefined, in Access this would cause the parameter entry popup window to appear.
SELECT list of fields or aggregating functions you want (comma-separated)
FROM list of tables the fields are in (comma-separated) and how to join the tables
WHERE list of conditions to filter the data (separated by AND or OR)
Example:
SELECT tblStores.Name, tblStores.Description, MIN(tblCustomers.age)
FROM tblStores INNER JOIN ( tblPurchases INNER JOIN tblCustomers on tblPurchases.customerID = tblCustomer.customerID) ON tblStores.storeID = tblPurchases.storeID
WHERE (tblStores.Name = inputStoreName);
I recommend checking W3 schools. They are usually helpful for most programming tasks. If you provide more info about your database, we can provide more directed help.
I have the following data structure
Store
Id
StoreName
Product
Id
Name
StoreId
Category
Id
Name
ProductCategory
Id
ProductId
CategoryId
Deal
Id
Name
DealCategory
Id
DealId
CategoryId
My requirement is to get a collection of strings representing categories and then query for stores which have a product or a deal in any of the given categories. Can anyone help as I am stumped. I get the right results if I don't filter by categories but the filter bit just seems to fail s I get no records back and I am certain that there is at least one Store with both a product and a deal in the given categories.
Here is my code so far, if I remove the where clause, I get the right data i.e. all the Stores (that have Deals or Products?! I haven't tested this discrimination yet).
from s in ctx.Store
join d in ctx.Deals on s.ID equals d.StoreID
join l in ctx.Products on s.ID equals l.StoreID
where d.DealCategories.Any(dc => categoriesList.Contains(dc.Category.Name.ToLower()))
group s by s.ID into sg
select new { Store = sg.FirstOrDefault() };
I have three table in my database.
Customers, which contains detaills of each client, such as name, phone number ...
Products, containing detaills of each product.
each time a client requests a product, a new line is inserted in the third table Orders.
the table Orders contains the customer id (foreign key), the product id (foreign key) and the quantity desired.
what I'm looking to do is to creat a report based on the Orders table, that shows me for each Client all the Orders that he has made.
I'm working on ms access 2007.
please help me !!!
Create a query based on the orders table joined to the customer table. Use the query design window to build the query. You can then base your report on the query, using grouping to get the customer details at the top of the group and the prder details as lines within the group. Use the report wizards.
Ok I have the solution.
I created a form with this record source:
SELECT
DISTINCT Costumers.Code, Costumers.Name, Costumers.phone
FROM
Costumers INNER JOIN Orders
ON Costumers.ID=Orders.IdCostumer;
then I've created a subreport with this record source:
SELECT
[Costumers].[Code],
[Orders].[Code],
[Products].[Description],
[Orders].[Quantity]
FROM
Products INNER JOIN
(Costumers INNER JOIN Orders ON Costumers.ID=Orders.IdCostumer)
ON Products.ID=Orders.IdOrder;
and that's working the way I want.
thank you for your interest !!!
:-)
I am using Entity Framework 4.1 using the Code First approach. I have two entities that exhibit a parent-child relationship. To provide a concrete example, imagine I have a Category entity that has zero-to-many Product entities associated with it. I have set up navigation properties on both sides (in my example, the Category entity would have an ICollection<Product> property while the Product entity has a Category property).
Now, when I get Category entities I want to also get back a count of the number of children records for each category. I am aware I can do:
Category category = dbContext.Categories.Single(...);
int productCount = category.Products.Count();
But I am concerned because the resulting SQL that gets sent to the database depends on whether I use lazy or eager loading.
In the first case (lazy loading), the call to the Products collection prompts EF to run a SQL query like:
SELECT ... all columns ...
FROM Products
WHERE CategoryID = #CategoryID
In the second case (eager loading), the products are loaded when the category information is retrieved so there is no second query to the database, but the downside is that if I'm not at all interested in products (other than their count) then I'm bringing back a lot of unneeded data.
What I'd like it to have the best of both worlds: namely, the ability to have just one database query and one that uses SELECT COUNT(*) rather than one that gets all of the columns from the table. In short, I'd like SQL like the following to be sent to the database:
SELECT ... all category columns ...,
(SELECT COUNT(*) FROM Products p WHERE p.CategoryID = c.CategoryID)
FROM Categories c
WHERE c.CategoryID = ...
Is that at all possible with EF or is what I want a pipe dream?
Not sure, but maybe try this:
var result = db.Categories.Where(x => x.CategoryId == categoryId)
.Select(y => new
{
Count = y.Products.Count(),
Category = y
})
.Single();
//result.Count
//result.Category
Yes, this is possible with EF. You can also create a view model to show the information with the child counts as properties. This article cover how to do that.
http://www.ozkary.com/2015/04/entity-framework-associated-table.html