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Unique column (algorithm)

  • July 3, 2006 at 1:10 pm

    #60923

    Hi,

    I am trying to find a solution to generate a hash key for a given string (CompanyName) and store that information (HashKey). For example,

    CREATE TABLE dbo.Example (CompanyName VARCHAR(250), HashKey CHAR(10))

    INSERT INTO dbo.Example (CompanyName) VALUES('Microsoft')

    SELECT CompanyName, HashKey FROM dbo.Example

       Microsoft, BIXY38F24K

    INSERT INTO dbo.Example (CompanyName) VALUES('Microsoft Inc.')

    SELECT CompanyName, HashKey FROM dbo.Example

       Microsoft, BIXY38F24K

       Microsoft Inc., BIDXY3FE24

    INSERT INTO dbo.Example (CompanyName) VALUES('Intel Inc.')

    SELECT CompanyName, HashKey FROM dbo.Example

       Microsoft, BIXY38F24K

       Microsoft Inc., BIDXY3FE24

       Intel Inc., OI3MXK95K3

    Does anyone have this implemented?

    Thank you,

    R

  • July 3, 2006 at 1:31 pm

    #647275

    Have you looked at the the CHECKSUM function and the HashBytes function (HashBytes may only be in 2005 I can't remember) anyway both these built in fucntions can be used to create a hash

     

    hth

     

    David

     

  • July 3, 2006 at 1:57 pm

    #647282

    Thank you David.

    I think CHECKSUM function should be good enough for what I am looking for.

  • July 4, 2006 at 11:51 am

    #647381

    CHECKSUM and BINARY_CHECKSUM are very poor hashes. Don't be surprised if you find almost 1% collisions. But as long as you don't rely on them for uniqueness, they can help in the creation of compact indexes for exact-lookup (not for key-range lookups).

     

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