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Message Posted: Wed, 25 Aug 2004 @ 10:17:07 GMT


     
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Subj:   Re: MULTISET Vs SET tables
 
From:   Frank O Connor

Rajah

The advantage of multiset tables is that they do not check for duplicate rows and this means that inserting data is quicker.

However, there can be a downside. For any given load, you may not load duplicates. You must be certain of that fact or else duplicate rows may be inserted. In addition, you may need to build in some form of checking to ensure that the same data is not loaded twice.

One level of protection is to add the teradata system time to each row. So, for a given INSERT/SELECT, the same system time will be added to each row. This provides a level of protection in that you can identify the second spurious load.

For Fastload and Multiload, you may have to accept in external date and time values to ensure you get a constant time for the load.


Hope this helps

Frank



     
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