Collection inside collection in sql server view

Posted on 2014-10-22
Last Modified: 2016-02-18
I have two tables. relation 1:N. when I create a view, I got one record for each item in the N table. How could I get a single record with a collection of the N table inside the first record? Is it possible?
From this view, we will create a stored procedure and mapped it with EF 6 to use into a c# web app.

thx in advance
Question by:Deraldo Silva
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LVL 50

Expert Comment

by:Vitor Montalvão
ID: 40396532
A GROUP BY clause will do the trick. You just need to decide if you want the MIN or MAX account:
SELECT users.Name, MAX(accounts.Account)
FROM accounts
	INNER JOIN users ON (accounts.userid = users.userid)
GROUP BY users.Name

Open in new window


Author Comment

by:Deraldo Silva
ID: 40396538
Hi Vitor, thx for your attention.
with this query I got the number of accounts that a user owns. I need this (in c# terms)

public class User
  public string Name { get; set; }
  public ICollection<string> accounts { get; set; }
[ {"nome1", [{"1"}, {"2"},{"3"},{"4"}]}, {... }]

LVL 50

Expert Comment

by:Vitor Montalvão
ID: 40396585
Deraldo, I'm afraid I can't help you with C#. I work only with SQL Server. Sorry.
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Author Comment

by:Deraldo Silva
ID: 40396600
Vitor, I do not have any question about c#, it's an example. because of this, I put two different examples, in  c# and in json.
ok. let me explain better.
My question is about sql server.
as I show in the picture, when i did my view, the sql is

SELECT        dbo.USERS.Name, dbo.ACCOUNTS.Account
                         dbo.USERS ON dbo.ACCOUNTS.UserID = dbo.USERS.UserID

but, with this query I got this result
Nome1 1
Nome1 2
Nome1 3
Nome1 4

If I have several fields in the Users table, these fields will be repeated, for all accounts, right? like this
Nome1 f1 f2 f3 f4 f5 f6 1
Nome1 f1 f2 f3 f4 f5 f6 2 and so on.

what I want: a single record where the accounts is another record set, inside the first one.

I don't know if it is possible.
maybe a select inside a select.
LVL 50

Expert Comment

by:Vitor Montalvão
ID: 40396609
Deraldo, can you post an example of the output you want?
Maybe it's better for me to understand with an example.

Author Comment

by:Deraldo Silva
ID: 40396696
thats the problem. I don't know how to show you the example as a sql result. I think that there is no such thing in sql. a recordset inside an record. a list as field element. wow! maybe converting one recordset into a xml value before output. So the user record, with all its fields and one field will be an xml with several accounts inside it.
is it possible with one view? or one stored procedure?

sorry for the inconvenience, this is like an handshake between two different expertises.
LVL 50

Accepted Solution

Vitor Montalvão earned 500 total points
ID: 40396702
SQL Server it's good to return data but for formatting I would prefer a program language or a reporting tool.
What I understood is that you want something like:
Nome1 f1 f2 f3 f4 f5 f6 1
Nome2 f1 f3 f5 f7 f8 f9 1
Nome3 f0 f2 f4 f6 f8 f9 1

If so, the only think SQL Server can do is to return it like:
Nome1 f1 f2 f3 f4 f5 f6 1
Nome1 f1 f2 f3 f4 f5 f6 2
Nome1 f1 f2 f3 f4 f5 f6 3
Nome1 f1 f2 f3 f4 f5 f6 4
Nome2 f1 f3 f5 f7 f8 f9 1
Nome2 f1 f3 f5 f7 f8 f9 2
Nome3 f0 f2 f4 f6 f8 f9 1

And then you format it as you need (suppress repeating values?).

Author Closing Comment

by:Deraldo Silva
ID: 40396727
yeah. that's what I realize.

anyway, thx for your attention.
LVL 29

Expert Comment

by:Olaf Doschke
ID: 40396788
Linq can do what you need, more precise the linq extension methods, not a linq query.
            using (var entities = new YourDatabaseEntities())
                Users = new Collection<User>(
                    entities.users.Select(usr => new User
                        Name =  usr.UserName,
                        Accounts = usr.accounts.Select(acc => new Account
                            AccountNo = acc.AccountNumber

Open in new window

The User class then will need to have a string Name property and a IEnumerable<Account> Accounts property.
Bye, Olaf.

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