Comments on: NULL is not zero! http://blog.tanelpoder.com/2009/12/30/null-is-not-zero/?utm_source=rss&utm_medium=rss&utm_campaign=null-is-not-zero Oracle, Exadata, Performance, Troubleshooting - Mobile Life and Productivity. Wed, 08 Feb 2012 08:03:50 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Ericcn http://blog.tanelpoder.com/2009/12/30/null-is-not-zero/comment-page-1/#comment-3591 Ericcn Tue, 12 Jan 2010 04:44:40 +0000 http://blog.tanelpoder.com/?p=518#comment-3591 Oh, yes. Null value wouldn't be counted in for the grouping function, like avg(). Oh, yes. Null value wouldn’t be counted in for the grouping function, like avg().

]]> By: Log Buffer #174: a Carnival of the Vanities for DBAs | The Pythian Blog http://blog.tanelpoder.com/2009/12/30/null-is-not-zero/comment-page-1/#comment-3569 Log Buffer #174: a Carnival of the Vanities for DBAs | The Pythian Blog Fri, 08 Jan 2010 19:46:38 +0000 http://blog.tanelpoder.com/?p=518#comment-3569 [...] begin with nothing. Tanel Poder wishes to remind us that NULL is not zero!, with, “an example [of] how misunderstanding NULLs may cause your application to return [...] [...] begin with nothing. Tanel Poder wishes to remind us that NULL is not zero!, with, “an example [of] how misunderstanding NULLs may cause your application to return [...]

]]> By: Hans Forbrich http://blog.tanelpoder.com/2009/12/30/null-is-not-zero/comment-page-1/#comment-3503 Hans Forbrich Wed, 30 Dec 2009 16:34:29 +0000 http://blog.tanelpoder.com/?p=518#comment-3503 Oracle made a decision years ago to equate null to 'empty string'. I believe that has had an influence on the challenge we face with NULL in general. The habit of defining a default value for 'unknown' has been ingrained in IT for years. Using the reverse logic, it is easy to see why people jump to the conclusion that null might be a specific value. You provide a great and simple example to present to students. Oracle made a decision years ago to equate null to ‘empty string’. I believe that has had an influence on the challenge we face with NULL in general.

The habit of defining a default value for ‘unknown’ has been ingrained in IT for years. Using the reverse logic, it is easy to see why people jump to the conclusion that null might be a specific value.

You provide a great and simple example to present to students.

]]> By: Louis Frolio http://blog.tanelpoder.com/2009/12/30/null-is-not-zero/comment-page-1/#comment-3502 Louis Frolio Wed, 30 Dec 2009 15:25:05 +0000 http://blog.tanelpoder.com/?p=518#comment-3502 Having been in this business for 13 years I am still shocked to find folks who don't understand what "null" really means. In addition, as illustrated here how you form your query will have an impact on how nulls are handled. I have found (working with many software engineering teams) that in some scenarios it is much more efficient to persist values to represent nulls and then searching on that value to find the nulls. Think about what Oracle's query optimizer does with a query where ".. table.column is null .." You are looking for nothing and there can be cases where a full table scan might be implemented. Having been in this business for 13 years I am still shocked to find folks who don’t understand what “null” really means. In addition, as illustrated here how you form your query will have an impact on how nulls are handled. I have found (working with many software engineering teams) that in some scenarios it is much more efficient to persist values to represent nulls and then searching on that value to find the nulls. Think about what Oracle’s query optimizer does with a query where “.. table.column is null ..” You are looking for nothing and there can be cases where a full table scan might be implemented.

]]> By: Joel Slowik http://blog.tanelpoder.com/2009/12/30/null-is-not-zero/comment-page-1/#comment-3501 Joel Slowik Wed, 30 Dec 2009 13:44:45 +0000 http://blog.tanelpoder.com/?p=518#comment-3501 The nvl() function is handy in this case to define what a null could mean in an aggregate function. I use the nvl() function all the time to prevent misinterpretation of null. The nvl() function is handy in this case to define what a null could mean in an aggregate function. I use the nvl() function all the time to prevent misinterpretation of null.

]]> By: Tanel Poder http://blog.tanelpoder.com/2009/12/30/null-is-not-zero/comment-page-1/#comment-3499 Tanel Poder Wed, 30 Dec 2009 12:29:21 +0000 http://blog.tanelpoder.com/?p=518#comment-3499 ...the important part is to make an informed decision, whether a value should be set to 0 or left NULL in case the value is "missing". And this comes directly from business requirements, it's not really a technical problem as such... …the important part is to make an informed decision, whether a value should be set to 0 or left NULL in case the value is “missing”. And this comes directly from business requirements, it’s not really a technical problem as such…

]]> By: Tanel Poder http://blog.tanelpoder.com/2009/12/30/null-is-not-zero/comment-page-1/#comment-3498 Tanel Poder Wed, 30 Dec 2009 12:27:14 +0000 http://blog.tanelpoder.com/?p=518#comment-3498 I'd say everywhere in the world! I’d say everywhere in the world!

]]> By: Ilmar Kerm http://blog.tanelpoder.com/2009/12/30/null-is-not-zero/comment-page-1/#comment-3495 Ilmar Kerm Wed, 30 Dec 2009 09:15:10 +0000 http://blog.tanelpoder.com/?p=518#comment-3495 Yes, in Estonia this topic needs a special attention in SQL courses :) Yes, in Estonia this topic needs a special attention in SQL courses :)

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