sql server - Create a view with ORDER BY clause

Question

I'm trying to create a view with an ORDER BY clause. I have create it successfully on SQL Server 2012 SP1, but when I try to re-create it on SQL Server 2008 R2, I get this error:

Msg 102, Level 15, State 1, Procedure TopUsers, Line 11
Incorrect syntax near 'OFFSET'.

The code to create the view is

CREATE View [dbo].[TopUsersTest] 
as 
select 
u.[DisplayName]  , sum(a.AnswerMark) as Marks
From Users_Questions us inner join [dbo].[Users] u
on u.[UserID] = us.[UserID] 
inner join [dbo].[Answers] a
on a.[AnswerID] = us.[AnswerID]
group by [DisplayName] 
order by Marks desc
OFFSET 0 ROWS

=====================

This is a screen shot of the diagram

I wish to return users' DisplayName and the UserTotalMarks and order this result desc, so the user with the biggest result with be on the top.

Answer 1

I'm not sure what you think this ORDER BY is accomplishing? Even if you do put ORDER BY in the view in a legal way (e.g. by adding a TOP clause), if you just select from the view, e.g. SELECT * FROM dbo.TopUsersTest; without an ORDER BY clause, SQL Server is free to return the rows in the most efficient way, which won't necessarily match the order you expect. This is because ORDER BY is overloaded, in that it tries to serve two purposes: to sort the results and to dictate which rows to include in TOP. In this case, TOP always wins (though depending on the index chosen to scan the data, you might observe that your order is working as expected - but this is just a coincidence).

In order to accomplish what you want, you need to add your ORDER BY clause to the queries that pull data from the view, not to the code of the view itself.

So your view code should just be:

CREATE VIEW [dbo].[TopUsersTest] 
AS 
  SELECT 
    u.[DisplayName], SUM(a.AnswerMark) AS Marks
  FROM
    dbo.Users_Questions AS uq
    INNER JOIN [dbo].[Users] AS u
      ON u.[UserID] = us.[UserID] 
    INNER JOIN [dbo].[Answers] AS a
      ON a.[AnswerID] = uq.[AnswerID]
    GROUP BY u.[DisplayName];

The ORDER BY is meaningless so should not even be included.

---

To illustrate, using AdventureWorks2012, here is an example:

CREATE VIEW dbo.SillyView
AS
  SELECT TOP 100 PERCENT 
    SalesOrderID, OrderDate, CustomerID , AccountNumber, TotalDue
  FROM Sales.SalesOrderHeader
  ORDER BY CustomerID;
GO

SELECT SalesOrderID, OrderDate, CustomerID, AccountNumber, TotalDue
FROM dbo.SillyView;

Results:

SalesOrderID   OrderDate   CustomerID   AccountNumber   TotalDue
------------   ----------  ----------   --------------  ----------
43659          2005-07-01  29825        10-4020-000676  23153.2339
43660          2005-07-01  29672        10-4020-000117  1457.3288
43661          2005-07-01  29734        10-4020-000442  36865.8012
43662          2005-07-01  29994        10-4020-000227  32474.9324
43663          2005-07-01  29565        10-4020-000510  472.3108

And you can see from the execution plan that the TOP and ORDER BY have been absolutely ignored and optimized away by SQL Server:

There is no TOP operator at all, and no sort. SQL Server has optimized them away completely.

Now, if you change the view to say ORDER BY SalesID, you will then just happen to get the ordering that the view states, but only - as mentioned before - by coincidence.

But if you change your outer query to perform the ORDER BY you wanted:

SELECT SalesOrderID, OrderDate, CustomerID, AccountNumber, TotalDue
FROM dbo.SillyView
ORDER BY CustomerID;

You get the results ordered the way you want:

SalesOrderID   OrderDate   CustomerID   AccountNumber   TotalDue
------------   ----------  ----------   --------------  ----------
43793          2005-07-22  11000        10-4030-011000  3756.989
51522          2007-07-22  11000        10-4030-011000  2587.8769
57418          2007-11-04  11000        10-4030-011000  2770.2682
51493          2007-07-20  11001        10-4030-011001  2674.0227
43767          2005-07-18  11001        10-4030-011001  3729.364

And the plan still has optimized away the TOP/ORDER BY in the view, but a sort is added (at no small cost, mind you) to present the results ordered by CustomerID:

So, moral of the story, do not put ORDER BY in views. Put ORDER BY in the queries that reference them. And if the sorting is expensive, you might consider adding/changing an index to support it.