Question : Index view won't accept outer joins

I have a view that I would like to create a index on. My database is on a MS SQL 2008 Server. The view contains an outer join, and that doesn't work in a index view. So my question is, how can I create an alternative, like an inner join, to my outer join?

The view is like this (abreviated):

create view [dbo].[vwProducts]
with schemabinding
as
select P.Itemno,
P.Name
from Products as P
left outer join dbo.WarehouseStock as WS on WS.ItemNo = P.ItemNo

where WS.ItemsRemaining > 5

Regards
Jens

Answer : Index view won't accept outer joins

Indexed Views With Outer Joins
By Jean Charles Bulinckx, 2005/05/19
Total article views: 10288 | Views in the last 30 days: 37
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Sometime ago I´m in trouble with a massive and large view. This monster was as slow a performing view as I've seen and I started to put in an effort to speed up the server and lower the response time.

First I considered creating some indexes on the view, but there a lot of limitations on indexed views. No unions, no sub-queries, no reference to other views and no OUTER JOINS! A legitimately needed left join was present in the view and any attempt to create a index raised a "not allowed construct" error. After hours of trial and error I managed to do it work. It's not at all an elegant approach, but it works for outer joins. Unions, sub-queries and temporary tables can be emulated by these outer joins, and these can emulate them too.
The Solution

The idea is quite simple. Just emulate a outer join with a inner join! Swamp the outer join with a inner join and put a isnull(table_id,0) at one side of the comparison. The code below shows a full example:

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CREATE TABLE Father                                                                                  (
   Father_id  smallint IDENTITY(1,1) PRIMARY KEY CLUSTERED,
	Father_Name varchar(50)
   )
GO                                                                                                 CREATE TABLE Son
  (
  Father_id  smallint, /*Foreign key*/
  Paternity varchar(50)
  )
GO
INSERT INTO Father values('Father 1')
INSERT INTO Father values('Father 2')
INSERT INTO Father values('Father 3')
INSERT INTO Son values(1,'Child 1A of father 1')
INSERT INTO Son values(1,'Child 1B of father 1')  
INSERT INTO Son values(2,'Child 2A of father 2')   
INSERT INTO Son values(null,'Child 0X of no father')   
GO
/* Test your tables */
SELECT f.father_id, f.father_name, s.father_id, s.paternity
 from father f
      INNER JOIN son s 
		      on s.father_id=f.father_id
GO
/* Test your tables twice*/
SELECT f.father_id, f.father_name, s.father_id, s.paternity
 from father f
       LEFT JOIN son s 
		      on s.father_id=f.father_id
/* Test your tables twice*/
SELECT f.father_id, f.father_name, s.father_id, s.paternity
 from father f
      RIGHT JOIN son s 
		      on s.father_id=f.father_id
GO
/* Yep, do u need to put the owners names to bind the view to the schema */
CREATE VIEW [dbo].[Family] WITH SCHEMABINDING 
AS
/* Yes! You are right this is equal to the select example ;) */
SELECT f.father_id, f.father_name, s.father_id as son_id, s.paternity
 from [dbo].[father] f
      INNER JOIN [dbo].[son] s 
		      on isnull(s.father_id, -255)=f.father_id
GO                                                                                                 SELECT * FROM Family
GO
/* Hey!!! It not worked! We are forgetting one important thing to do   */
/* we need a row at the father table to be the "null" or no father row */
SET IDENTITY_INSERT Father ON
INSERT INTO Father (Father_id, Father_name) values(-255,'No father')
SET IDENTITY_INSERT Father OFF
GO
/* Now create your indexes!!! */
CREATE  UNIQUE  CLUSTERED  INDEX [Pk_Paternity] 
   ON [dbo].[Family]([paternity]) 
	ON [PRIMARY]
GO
CREATE  INDEX [Pk_father_name] 
   ON [dbo].[Family]([father_name]) 
	ON [PRIMARY]
GO
INSERT INTO Son values(2,'Child 2B of father 2')
INSERT INTO Son values(2,'Child 2C of father 2')
INSERT INTO Son values(null,'Child 0Y of no father')
INSERT INTO Son values(null,'Child 0Z of no father')
GO                                                                                                 
SELECT * FROM Family
GO                                                                                                

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