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Query Plan?

  • November 6, 2011 at 6:58 pm

    #250370

    Greetings,

    I am learning about database index right now, thru reading "Stairway to SQL Server Indexes: Step 9..." http://www.sqlservercentral.com/articles/Stairway+Series/72441/. There is some thing I don't understand. It said with query below:

    SELECT C.LastName, C.FirstName, C.MiddleName, C.Title, H.SalesOrderID, H.OrderDate

    FROM Person.Contact C

    JOIN Sales.SalesOrderHeader H ON H.ContactID = C.ContactID

    WHERE Suffix is null

    ORDER BY Title

    the query plan would be as figured as number 5. And I already test it in SSMS.

    I thought the query plan should be still like figure 4 (not changing). This is because index IX_ContactID which added later does not give more advantage (lack field SalesOrderID to show for final output). How come with new index IX_ContactID and Clustered Index of table Contact, we can produce field SalesOrderID for final result?

    Please give me enlightenment here.

    Thanks in advance.

  • November 7, 2011 at 2:25 am

    #1403811

    Maybe post this in the comments of the article?

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass

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