Home Page for the TeradataForum

Archives of the TeradataForum

Message Posted: Wed, 16 Nov 2011 @ 11:13:04 GMT

  <Prev Next>   <<First <Prev

Subj:   Re: NOT ( columnname is NULL) condition in a LOJ
From:   Victor Sokovin

Anomy.Anom wrote:

  In an explain involving a LOJ , it reads something like this ...  

  NOT ( col1 ?is NULL) and then it mentions about doing the LOJ. I can understand the NOT NULL approach but its doing this even AFTER that column is already defined as NOT NULL in the DDL. Why have this NOT NULL check on a column that is guaranteed to be a NOT NULL 'by birth'  

When you deal with outer joins NULLs can appear in the result set of the query even for columns that are 'by birth' NULL-free. So far nothing surprising in the explain.

There is still a group of data modelers out there who spend their time eliminating poor NULLs from their models and databases because they read somewhere that NULLs are not so good. It is a rather useless approach if outer joins are going to be used.


  <Prev Next>   <<First <Prev
  Top Home Privacy Feedback  
Copyright for the TeradataForum (TDATA-L), Manta BlueSky    
Copyright 2016 - All Rights Reserved    
Last Modified: 15 Jun 2023