Question

I have a contracts table that is large and that we have many stored procedures that query for contracts with a status of Open. Less than 10% of the contracts are open and this number is shrinking as the DB grows. I thought I could create an Indexed view of the open contracts in order to speed up some of our queries. The problem is that the status is not on the contract table and I need a subquery to retrieve the data I want. (SQL Server then does a clustered index scan on the whole table in the queries I have looked at)

Here is the condensed version of the view (I removed the 30 other columns from the contract table)

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE VIEW [dbo].[vw_OpenContractsIndexed]
WITH SCHEMABINDING 
AS
SELECT     c.ContractID
FROM         dbo.NMPT_Contract AS c INNER JOIN
                      dbo.NMPT_ContractStatus AS cs ON c.ContractID = cs.ContractID AND cs.ContractStatusCreated =
                          (SELECT     MAX(ContractStatusCreated) AS Expr1
                            FROM          dbo.NMPT_ContractStatus AS cs2
                            WHERE      (ContractID = c.ContractID)) INNER JOIN
                      dbo.CMSS_Status AS s ON cs.StatusID = s.StatusID
WHERE     (s.StatusCode = 'OPN')

If I try to create an index on the view (unique clustered on contractid) I get the following

Creation Failed for Index
It contains one or more disallowed constructs. (Microsoft SQL Server, Error 1936)

From what I can gather it is the Max in the subquery that is the problem??

Other than putting the status on the contracts table (where I personally think it belongs) are there any suggestions for optimising this situation. Failing that will other versions of SQL Server allow this indexed view?

Answer 1

From TechNet regarding Indexed Views in SS 2000:

There are several restrictions on the syntax of the view definition.
The view definition must not contain the following:

COUNT(*)

ROWSET function

Derived table

self-join

DISTINCT

STDEV, VARIANCE, AVG

Float*, text, ntext, image columns

Subquery

full-text predicates (CONTAIN, FREETEXT)

SUM on nullable expression

MIN, MAX

TOP

OUTER join

UNION

You’re using MAX, and a subquery, both of which are not allowed.

To get advice on how to get around this, you need to share some data and what you are trying to do.