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Should it be allowed to have NULL values in a database?
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This article shows you how to use the Oracle Data Dictionary to obtain: table definitions, constraints, Indexes, views, sequences, triggers and PL/SQL functions and procedure.
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Is there a way to check to see if a system file exists in PL/SQL?
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Oracle defines a number of exceptions for me, like no_data_found. Why would I ever need to or want to define my own exceptions?
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my 2 cents on NULL values in a database
I strongly disagree with the conclusion of the article. Even if I could understand that “unknown” gender is somewhat confusing and could lead to poor data quality, it is highly irrelevant to fill all optional columns of your data with 0 or space. I hate much more queries like where x = ‘ ‘, but because a developer hated nulls at that time.
Also deeply stupid are datamodels where the child table (cardinality 1:0,n) has ID=-1 for inexistant childs, which is completely misleading, for both dba and optimiser.
I do not have nulls. The one I do not like too much is length(”) is null, but as written in doc 7,8,8i,9,10,11, it may change in a next release
December 8th, 2006, at 3:28 am #Nulls may be a problem to relational purists, but they are a practical neccessity for designing real systems for real people. The fact is that some values are in fact unknown. Will you prevent entry of the values that are known, just because some of the values are not known? And yes, nulls have their quirks (I wish that null=null), but the smart developer understands how nulls work and takes them into account.
December 8th, 2006, at 7:52 am #Some people don’t like NULLs, others like NULLs to the degree of inventing a new number called “nullity”. Check this out: Nullity - the Nonsense Number.
December 8th, 2006, at 12:30 pm #this about nan, not null
http://preview.tinyurl.com/ybmkhh
December 9th, 2006, at 12:29 am #[i]an excellent job of demonstrating what total innumerate idiots reporters are.[/i]
December 9th, 2006, at 12:31 am #