sql query optimization for deduplication.

• Roger Jones

  Grasshopper

  Points: 10

  More actions

  June 21, 2013 at 8:59 am

  #150372

  Hi All,

  I have a query for de duplicating messages based on unique hash and then sorting and paging it, i was wondering how I can optimize it better.

  Hash and Name column in the Message table are non clustered indexes defined with storeid, folderid, Hash or Name(either)

  The only thing i see problematic is an index scan but that is same even if i remove the deduplication cte and do the main query on the Message table, i think that is more to do with select *

  Any help will be greatly appreciated.

  With DeduplicatedMessages as

  (

  select * from Message

  JOIN

  (

  SELECT MAX(MessageId) as UniqueMessageId

  FROM Message

  where StoreId=210 and FolderId=24541

  GROUP BY Hash

  ) as UniqueMessages ON

  Message.Messageid = UniqueMessages.UniqueMessageId

  )

  select * from (select ROW_NUMBER() over (order by Name ASC) as RI, * from DeduplicatedMessages) as SUB where sub.RI >= 0 and sub.RI <=1000

  Thanks

• Sean Lange

  SSC Guru

  Points: 286602

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  June 21, 2013 at 9:04 am

  #1626364

  In order to help we will need a few things:

  1. Sample DDL in the form of CREATE TABLE statements

  2. Sample data in the form of INSERT INTO statements

  3. Expected results based on the sample data

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