How Do I Get Data From A Many To Many Related Table Using Sql Or Linq To Entities

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I have table related to two tables which is a many to many relationship. For eg: I have a user, product and userproducts table that contains these columns:

User
id
username
email
lastname

Product
id
userid int foreign key references user(id)
name
quantity

Userproducts
id
userid int foreign key references user(id)
productid int foreign key references Product(id)

Now, how do i get the username, last name and product name from the users and products table respectively that does not exist in the Userproducts table.

I have a method that list all the users products from the Userproductstable, but it is really giving me a tough time to get it the other way around.

Please, any help on how to do this either in EF or pure sql query. Thanks

Posted 7-Apr-15 9:26am

Member 10250878

Updated 7-Apr-15 9:30am

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Maciej Los 7-Apr-15 16:10pm

What have you tried? Where are you stuck?

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Caldazar87 · Accepted Answer · 2015-04-07T09:46:00

Hello,

If I understood you correctly, you need all combinations of users and products that doesn't exist in Userproducts table?

If that is correct, then this query should give you all required results:

SQL

Select u.username, u.lastname, p.name
From User as u, Product as p
Where not exists 
(Select * From Userproducts as up Where up.userid=u.id and up.productid=p.id)

If what you require is separately for users and for products, then it is even easier:
Users:

SQL

Select u.username, u.lastname
From User as u
Where u.id not in
(Select up.userid From Userproducts)

Products:

SQL

Select p.name
From Product as p
Where p.id not in
(Select up.productid From Userproducts)

Hope it helped.
Regards,