Click here to monitor SSC
SQLServerCentral is supported by Red Gate Software Ltd.
 
Log in  ::  Register  ::  Not logged in
 
 
 

Indexed Views With Outer Joins

By Jean Bulinckx,

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:

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                                                                                                

Conclusions

Before your start to put indexes at all views, try use all your other tricks to enhance performance first. Use tables indices, normalization, disk IO, etc. Indexed views are one more tool at hand and this article is just one more tip to help you use them.

Total article views: 13397 | Views in the last 30 days: 24
 
Related Articles
FORUM

Deleting Grandfather, father, child records

Hi All. Can someone help with the following please. 3 tables BudgetCategory, Budget and BudgetHold...

FORUM

Fathers

OK, I'm late. It was Father's Day last Sunday, but to be fair, I'd just returned from Mexico and...

FORUM

How to avoid cursor for parent-child inserts

How do you handle multi-table inserts which rely on the ID created in previous insert

FORUM

Child and parent Relation

Child and parent Relation

FORUM

To Parent/Child or Not To Parent/Child

looking for strategy on whether or not to create child tables

Tags
indexing    
sql server 7    
 
Contribute

Join the most active online SQL Server Community

SQL knowledge, delivered daily, free:

Email address:  

You make SSC a better place

As a member of SQLServerCentral, you get free access to loads of fresh content: thousands of articles and SQL scripts, a library of free eBooks, a weekly database news roundup, a great Q & A platform… And it’s our huge, buzzing community of SQL Server Professionals that makes it such a success.

Join us!

Steve Jones
Editor, SQLServerCentral.com

Already a member? Jump in:

Email address:   Password:   Remember me: Forgotten your password?
Steve Jones