Can you please differentiate blw Unique Clustered Index and Non Unique Clustered Index. RRS feed

  • Question

  • Can you please differentiate b/w the following:

    Unique Clustered Index
    Non Unique Clustered Index
    and explain what are these?


    Nagaraju K.

    • Edited by Raj. K Thursday, March 15, 2012 7:23 AM
    Wednesday, March 14, 2012 4:26 PM


  • the difference is that the index key is unique for one and not for the other.  In the case of a non-unique key, sql server has to create a unique key by appending some other values to the key.  This adds additional overhead for both performance and storage.  Additonally SQL Server could pontentially use a less efficient query plan for queries becuase it doesnt know the key used in the predicate is unique.  Always use a unique index where available, as this will help to optimize performance, save storage, and gives you insight into the data without querying the table.


    • Proposed as answer by Naomi N Tuesday, March 20, 2012 8:42 PM
    • Marked as answer by KJian_ Wednesday, March 21, 2012 3:32 AM
    Wednesday, March 14, 2012 4:57 PM

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