Okay so I have a database that has a Projects, Users and ProjectMembers table, the Projects table has an ID column and ProjectOwner column which is a foreign key from the Users table, the Users table has ID, username columns and the ProjectMembers table has an ID, ProjectID and UserID column with the later 2 columns being foreign keys from the Projects table and Users table.
Basically the project is something that manages projects, a user can create a project which makes them the owner and then other users can be assigned to that project which adds a record to the ProjectMembers table.
I'm trying to write a linq query that selects all records from the Projects table where a specific user isn't the ProjectOwner but they are a ProjectMember in the ProjectMembers table?
I've made various attempts but so far haven't been able to get the query right.
Something like this should work:
from p in Projects
join m in ProjectMembers on m.ProjectID equals p.ID
where m.UserID == userID && p.ProjectOwner != userID
group p by p.ID
select p
You can make several from clauses:
from e1 in table1
from e2 in table2
where e1.key == e2.id
select e1.name
Try this:
from x in Users
where ProjectMembers.Any(y => y.UserID==x.ID) &&
!ProjectOwners.Any(z => z.ProjectOwner==x.ID)
select x;
Related
I'm creating a desktop application. I have 3 table (part time employees table, full time employees table and department table). The ID on department table is the foreign key.
I have created a connection string in my class. I'm trying to loop through the tables to get all departments that are assigned to employees, if a department is not assigned (delete it). I have the code in sql, but I want it in c#. Below is the sql code.
SELECT DepartmentName, DepartmentAddress
FROM Department
WHERE ID IN
(SELECT DISTINCT(ID)
FROM
PartTimeEmployees
);
If you simply want to DELETE departments that don't have a related employee, you can use an EXISTS:
DELETE D
FROM dbo.Department D
WHERE NOT EXISTS(SELECT 1
FROM dbo.Employee E
WHERE E.DepartmentID = D.ID);
There's no need to go any kind of "looping", as SQL is far better at doing these operations in a set-based way.
If deleting department not in part time employees table or full time employees table then you can get the department list as -
var departmentToDelete = departments.Where(d => !PartTimeEmployees.Any(emp => emp.DepartmentId == d.Id) && !FullTimeEmployees.Any(emp => emp.DepartmentId == d.Id)).ToList();
I have a table Users which contain user information. I have a table Products which contain product information. I have a table called UserProduct which acts as a junction table and whose fields are UserId and ProductId. I am using a Entity Framework database first approach.
I want to outerjoin using Linq to find the following data.
All Users in the Users table.
All Users who have bought a particular product in terms of a Boolean called isPurchased.
My thinking was to left outer join table User with UserProduct and get all users and whether they have a product something like this.
var result = from a in Users
join b in UserProduct(Not available through EF) on a.Id equals b.prodId into group1
from g1 in group1.DefaultIfEmpty()
select new
{
id = g1.Id,
isPurchased = g1.prodId != null
}.ToList();
However in EF mapping, the object UserProduct is not created and so I cannot use it directly in my Linq query? So how do I go about this? Is there a way I can use linq to join tables with the actual table name(UserProduct) instead of joining entities?
Assuming Users contains a property List<Products> products to represent the junction information, and a variable boughtProductId to represent the particular product:
var result = from u in Users
let isPurchased = u.products.Any(p => p.Id == boughtProductId)
select new {
id = isPurchased ? boughtProductId : null,
isPurchased
}.ToList();
I have 2 tables. One is a user table that holds userid and userSelection(foreign key to another table) both are primary keys so multiple rows for a user.
The 2nd table holds columns with it's primary id being userSelection.
I want to retrieve all the userSelection rows that a userId has from the 2nd table. I want to use linq lambda expressions too.
I have it working in sql jsut can't convert it for use in c#.
Select * From column
where colID in (
select colId from users
where userID = 'someUser')
Thanks
Assuming you're using Entity Framework, what you're really looking for is an inner join. it would look something like this:
from c in context.Column
join u in context.Users on c.ColId equals u.ColId
where u.UserId = 'SomeUser'
select c;
as a lambda that is something like (syntax might be lacking something) (no where clause here, but easily added)
context.Column.Join( context.Users, u => u.ColId, c => c.ColId).Select
Change this code to two parts
Select * From column
where colID in (
select colId from users
where userID = 'someUser')
First part to get colId list:
var colIds = context.users.Where(x=>x.userID == "someUser").Select(x=>x.colId).ToList();
Second part to get the result use Where and List.Contains
// IQueryable result
var result = context.column.Where(x=>colIds.Contains(x.colID));
You can use it inline, but I recommend it to be two parts.
I have 3 Tables called Invoice, Customer and Company. I want to merge this 3 tables into single using Query. In Invoice Table contain Customer Id and Company Id. How to Join 3 tables ?
I tried Invoice and Customer Table working fine with this query. But I dont have idea to add 3rd table with this.
SELECT RPT_Invoice_Less.InvoiceNumber, RPT_Invoice_Less.Terms,
RPT_Invoice_Less.Invoicedate, RPT_Invoice_Less.OurQuote,
RPT_Invoice_Less.SalesPerson, RPT_Customer.CustomerName,
RPT_Customer.CustomerId, RPT_Customer.ContactPerson,
RPT_Customer.BillingAddress, RPT_Customer.DeliveryAddress,
RPT_Invoice_Less.OrderNumber, RPT_Invoice_Less.ShippingBy,
RPT_Invoice_Less.ShipReferenceNo, RPT_Invoice_Less.Notes,
RPT_Invoice_Less.Price, RPT_Invoice_Less.Discount,
RPT_Invoice_Less.Shipping, RPT_Invoice_Less.Tax,
RPT_Invoice_Less.GrandTotal, RPT_Invoice_Less.Company
FROM RPT_Invoice_Less
INNER JOIN RPT_Customer
ON RPT_Invoice_Less.CustomerId = RPT_Customer.CustomerId;
this code working fine for 2 tables
SELECT RPT_Invoice_Less.InvoiceNumber, RPT_Invoice_Less.Terms, RPT_Invoice_Less.Invoicedate, RPT_Invoice_Less.OurQuote, RPT_Invoice_Less.SalesPerson, RPT_Customer.CustomerName, RPT_Customer.CustomerId, RPT_Customer.ContactPerson, RPT_Customer.BillingAddress, RPT_Customer.DeliveryAddress, RPT_Invoice_Less.OrderNumber, RPT_Invoice_Less.ShippingBy, RPT_Invoice_Less.ShipReferenceNo, RPT_Invoice_Less.Notes, RPT_Invoice_Less.Price, RPT_Invoice_Less.Discount, RPT_Invoice_Less.Shipping, RPT_Invoice_Less.Tax, RPT_Invoice_Less.GrandTotal, RPT_OrionSystem.Company, RPT_OrionSystem.CompanyId
FROM RPT_Invoice_Less
INNER JOIN RPT_Customer
ON RPT_Invoice_Less.CustomerId = RPT_Customer.CustomerId
INNER JOIN RPT_OrionSystem
ON RPT_Invoice_Less.CompanyId = RPT_OrionSystem.CompanyId;
This code showing syntax error.
Help me to add 3rd Company table to this.
Supposing that you have a CompanyID field (or something like that) in the RPT_Customer table or in the RPT_Invoice_Less, it is just a matter to add another INNER JOIN
....
FROM ((RPT_Invoice_Less
INNER JOIN RPT_Customer
ON RPT_Invoice_Less.CustomerId = RPT_Customer.CustomerId)
INNER JOIN RPT_OrionSystem
ON RPT_Invoice_Less.CompanyID = RPT_OrionSystem.CompanyID)
I need to combine two or more table into one object by using C# 4,0... I wrote a class for a table which included simple select selectbyid insert update and update.... it works fine for single table... by the way I have two attribute which specifies table name column name and primarykey... by using all these I can create my simple methods but I need to select and update more table in one object or method... what should I do or what would you suggest about it...
Example:
users and customer table I have foreign keys which defined...
If you`re using linq to sql, you can join the other tables like
var q =
from s in db.Suppliers
join c in db.Customers on s.City equals c.City
select new {
Supplier = s.CompanyName,
Customer = c.CompanyName,
City = c.City
};
as just copy & paste from a sample of MSDN LINQ to SQL: .NET Language-Integrated Query for Relational Data