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From:Curtis Maurand Date:May 12 2003 2:33pm
Subject:Re: A seroius trouble with MySQL
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IIRC mysql enforces referential integrity for primary keys.  I don't think 
it allows the column to have NULL values.  I always try to use "int 
unsigned auto_increment not null primary key" for my primaries unless they 
are combinations of multiple columns and then it won't allow nulls as 
well.

Curtis

On Thu, 8 May 2003, Brian Reichert wrote:

> On Thu, May 08, 2003 at 03:12:45AM -0700, Nitin Nanivadekar wrote:
> > 1. the max () keyword reports 'different' resultsets
> > when following queries are sent to it,
> > 	a. select max(id) from table1;
> > 	b. select max(id) from table1 where id2=100;
> > in any condition (like the low resources etc.) i
> > should not get different results from seemingly
> > identical queries.
> 
> As you've described it, it's certainly possible; it completely
> depends on the table and it's contents.
> 
> > 2. i will also point one observation when i was
> > hacking the max () function. when there is an empty
> > set max() reports Null.
> 
> > this makes max() limited to
> > arithmatic ops only.
> 
> I don't understand this assertion; MAX() works with strings as well.
> 
> If stray NULL values are scaring you, try:
> 
>   select max(id) from mytable where id is not null;
> 
> See <http://www.mysql.com/doc/en/Problems_with_NULL.html>
> 
> Also consider using GREATEST().
> 
> > i am using max() to find the next
> > incremental primary key index for some other table. 
> > i am now seriously considering NOT using max() for
> > that reason after 1,. and 2. above.
> 
> Why would you have NULL values in your incremental primary key index
> column?  That (to me) implies a INT column, that should always have
> a value.
> 
> > pls. comment.
> > -nitin
> 
> 

-- 
--
Curtis Maurand
mailto:curtis@stripped
http://www.maurand.com


Thread
A seroius trouble with MySQLNitin Nanivadekar8 May
  • Re: A seroius trouble with MySQLBrian Reichert8 May
    • Re: A seroius trouble with MySQLCurtis Maurand12 May
  • Re: A seroius trouble with MySQLDan Nelson8 May
  • Re: A seroius trouble with MySQLKeith C. Ivey8 May
  • re: A seroius trouble with MySQLEgor Egorov10 May