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From:Paul DuBois Date:May 4 2001 5:38pm
Subject:RE: NULL value in VARCHAR fields
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At 10:28 AM -0700 5/4/01, Shankar Unni wrote:
>Paul DuBois writes:
>  > > At 8:21 PM +0200 5/3/01, stefan mojschewitsch wrote:
>>  >
>>  >using DEFAULT USER(), would be nice, but only constants are allowed.
>>  >to prevent inserting rows without iuser, i like to have this field
>>  >with NOT NULL restriction and default value NULL.
>  > That's a contradiction, isn't it? 
>No, it's not.
>It's an accepted idiom for declaring a *mandatory* column (I.e. one 
>that *has* to be specified in an insert). In fact, Or*cle (hiss) is 
>good enough to leave the default on the column as NULL if you don't 
>put an explicit default (and doesn't try to get too smart with 
>creating "reasonable" defaults), so if you declare a column as NOT 
>NULL and don't specify a default, it becomes mandatory to specify a 
>value for the column in INSERT statements.
>This is good programming practice, to document mandatory columns for 
>which there is *no reasonable default* (e.g. a U.S. bank account's 
>"associated taxpayer number" (SSN), to make a simplistic example - 
>it's not a primary key, but it's mandatory by law, and there's no 
>reasonable default for it - certainly not '').
>Shankar Unni

In that case, this section of the MySQL manual may be of interest:

@cindex default values, suppression
@cindex suppression, default values
You can configure @strong{MySQL} not to use @code{DEFAULT} column values for
non-@code{NULL} columns (that is, columns that are not allowed to be
@code{NULL}).  This causes @code{INSERT} statements to generate an error
unless you explicitly specify values for all columns that require a
non-@code{NULL} value.  To suppress use of default values, run
@code{configure} like this:

@tindex CXXFLAGS environment variable
@tindex environment variable, CXXFLAGS
@end example

Paul DuBois, paul@stripped
problems with privileges, MySQL for Windows 3.23.xxMySQL-Mail3 May
  • NULL value in VARCHAR fieldsstefan mojschewitsch3 May
    • Re: NULL value in VARCHAR fieldsPaul DuBois4 May
RE: NULL value in VARCHAR fieldsPaul DuBois4 May