How to improve SQL inner join performance? - sql

Question

How improve this query performance second table CustomerAccountBrand inner join
taking long time. I have added Non clustered index that is not use. Is this is split two inner join after that able concatenate?. Please any one help to get that data.
SELECT DISTINCT
RA.AccountNumber,
RA.ShipTo,
RA.SystemCode,
CAB.BrandCode
FROM dbo.CustomerAccountRelatedAccounts RA -- Views
INNER JOIN dbo.CustomerAccount CA
ON RA.RelatedAccountNumber = CA.AccountNumber
AND RA.RelatedShipTo = CA.ShipTo
AND RA.RelatedSystemCode = CA.SystemCode
INNER JOIN dbo.CustomerAccountBrand CAB ---- Taking long time 4:30 mins
ON CA.AccountNumber = CAB.AccountNumber
AND CA.ShipTo = CAB.ShipTo
AND CA.SystemCode = CAB.SystemCode
ALTER VIEW [dbo].[CustomerAccountRelatedAccounts]
AS
SELECT
ca.AccountNumber, ca.ShipTo, ca.SystemCode, cafg.AccountNumber AS RelatedAccountNumber, cafg.ShipTo AS RelatedShipTo,
cafg.SystemCode AS RelatedSystemCode
FROM dbo.CustomerAccount AS ca
LEFT OUTER JOIN dbo.CustomerAccount AS cafg
ON ca.FinancialGroup = cafg.FinancialGroup
AND ca.NationalAccount = cafg.NationalAccount
AND cafg.IsActive = 1
WHERE CA.IsActive = 1

Answer 1

From my experience, the SQL server query optimizer often fails to pick the correct join algorithm when queries become more complex (e.g. joining with your view means that there's no index readily available to join on). If that's what's happening here, then the easy fix is to add a join hint to turn it into a hash join:
SELECT DISTINCT
RA.AccountNumber,
RA.ShipTo,
RA.SystemCode,
CAB.BrandCode
FROM dbo.CustomerAccountRelatedAccounts RA -- Views
INNER JOIN dbo.CustomerAccount CA
ON RA.RelatedAccountNumber = CA.AccountNumber
AND RA.RelatedShipTo = CA.ShipTo
AND RA.RelatedSystemCode = CA.SystemCode
INNER HASH JOIN dbo.CustomerAccountBrand CAB ---- Note the "HASH" keyword
ON CA.AccountNumber = CAB.AccountNumber
AND CA.ShipTo = CAB.ShipTo
AND CA.SystemCode = CAB.SystemCode