why using different executed plan ?

• tramp168.my265

  SSC Journeyman

  Points: 83

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  April 10, 2009 at 3:35 am

  #73600

  In the personnel table , there is EmpCode, DeptCode and others fields, I created a clustered index on EmpCode,a non-clustered index on DeptCode, and some other indexs on other fields. I run below tow queries,but they use different Executed plan,the first query is used Table Scan ,the second query is used index seek,Could you please tell reason?

  select * from Personnel where DeptCode='SE665' ---Table Scan

  select * from Personnel where DeptCode='Dp028' ---index seek

  Thanks

• Gail Shaw

  SSC Guru

  Points: 1004504

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  April 10, 2009 at 3:43 am

  #975627

  Selectivity and the number of rows that the optimiser thinks will be returned.

  http://sqlinthewild.co.za/index.php/2009/01/09/seek-or-scan/

  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
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