SQL Server 2005 Index

We have a table that contains address information.  It has a primary key, called building code, and then the country, state, city, street and building name.  I'm using this table to populate a series of drop down menus dynamically when a user selects the parent drop down.  So if they select country, states are populated, selects state, cities are populated, etc.  When a user selects a country, the state, city, and street queries run pretty quickly but it takes almost 15 seconds to load building name.  I'm trying to figure out how to properly index this table to optimize the query.  We're planning on breaking the table out into separate entities but I'm just trying to see if there's a quick fix for the time being.

Here's the query I'm using
DECLARE @searchType            VARCHAR(15)
DECLARE @country            VARCHAR(100)
DECLARE @state                  VARCHAR(100)
DECLARE @city                  VARCHAR(100)
DECLARE @street                  VARCHAR(100)

SET @searchType = 'building'
SET @Country = 'UNITED STATES OF AMERICA'
SET @State = 'All'
SET @city = 'All'
SET @street = 'All'


SELECT DISTINCT
      BC.BuildingCode,
      BC.BuildingName
FROM        
      t_ResourceLocationAssignment AS RLA INNER JOIN
      t_CorporateDirectory_BuildingCode AS BC ON LEFT(RLA.mailCode,7) = BC.BuildingCode
WHERE
      BC.Country = (CASE WHEN @Country IN('All','') THEN BC.Country ELSE @Country END)
AND
      BC.State = (CASE WHEN @state IN('All','') THEN BC.State ELSE @State END)
AND
      BC.City = (CASE WHEN @city IN('All','') THEN BC.City ELSE @City END)
AND
      BC.StreetAddress = (CASE WHEN @street IN('All','') THEN BC.StreetAddress ELSE @street END)
AND
      BC.BuildingName <> ''
ORDER BY
      BC.BuildingName
stretch73Asked:
Who is Participating?
 
Lara FConnect With a Mentor EACommented:
I would suggest replacing all "case" with "isnull"

BC.Country = (CASE WHEN @Country IN('All','') THEN BC.Country ELSE @Country END)

--- redefine all variables as
if @Country in ('All','')  set @Country=null
-- then use
where BC.Country= isnull(@Country,BC.Country)

and instead of
 AND BC.BuildingName <> ''
use
AND BC.BuildingName  > ''
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Raja Jegan RSQL Server DBA & ArchitectCommented:
Since you have the below statement in your query

AND BC.BuildingName <> ''
ORDER BY BC.BuildingName

To increase performance of ORDER BY clause, creating an index on BuildingName would improve the performance a little bit.
But checking BuildingName <> '' would force a table scan thereby reducing the performance and inefficient usage of indexes..
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stretch73Author Commented:
I have an index on building name.  I'd really like to bring back records that don't have a ' ' value, is there a more efficient way of doing that?
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Raja Jegan RSQL Server DBA & ArchitectCommented:
>> I'd really like to bring back records that don't have a ' ' value, is there a more efficient way of doing that?

Nope, this search condition ideally would go for a table scan.

>> LEFT(RLA.mailCode,7) = BC.BuildingCode

Above condition would also force a table scan.
And both scenarios can be handled only by performing change in database design.
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stretch73Author Commented:
I had to add a LEN() to this:

AND BC.BuildingName  > ''

But this answer got me a significant performance improvement.
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