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Performance issue with Join on Computed Column

    Question

  • When joining with Persisted Computed Column I see performance degradation. For testing purpose I created another column in the table with same value that is in the Computed Column and the result comes very fast when I join against this new column. In the Execution Plan I see the Number Of execution is same as the number of records being returned when I am joining against this Computed Column which is very high.

    The expression for Computed Column is :

    [Id] 

    AS (([Code]+'_')+CONVERT([varchar](10),[MiddletierId],(0))) PERSISTED NOT NULL,

    What is the reason behind this performance degradation ?

    Thanks!!

    Monday, January 21, 2013 5:57 PM

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