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Message Posted: Mon, 16 Jan 2012 @ 13:48:29 GMT


     
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Subj:   Re: Compress Null value
 
From:   Machha Narayan Rao Naidu

Hi,

You will not get any significant changes in terms of Disk space while compressing NULL. If the no. of NULL's are large then you can see a little changes probably.

Below is the chart From Teradata manual on % Compression.

The following table shows example compressibility for fields of 1 and 4 bytes. "Percent compression" is the savings when considering the compressed size in comparison to the uncompressed size.

                    Frequency of
     Field Width    Single Value      Percent
     (Bytes)        (and NULL)        Compression
        1               20%              7%
        1               50%             37%
        1               80%             67%
        4               20%             17%
        4               50%             47%
        4               80%             77%

Note that the compression savings are for a particular column. Overall system savings is dependent on the number of columns that are compressed and the individual savings from each column.


Thanks

Machha



     
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