Posted by Jerry Stuckle on 01/23/06 04:24

Dave Smithz wrote:
> Thanks for the input.
>
>>OK so you want to subvert the normalization your database. This is
>>marginally more acceptable than cross-posting.
>
> Did not understand the first sentence. Is this a good or bad thing?
>
>>So that rules out subselects.
>
> Yes it is annoying that I have to support MySQL 3
>
>
>>
>>Messy if you only want to find out whom has not attended:
>>
>>SELECT a.student_id
>>FROM students a LEFT JOIN studentclasslink b
>> ON a.student_id=b.student_id
>>HAVING b.student_id IS NULL
>
>
> Good point in finding how many members have not attended. The SQL I gave was
> to more demonstrate my problem. Even with the above code, I still do not
> know how I apply this to an update situation.
> My worse case scenario is to in the PHP code store the row id's of the rows
> that need to be updated. But I was thinking there should be an SQL method.
>
>
>>As to what you do next - I guess you already know that since you posted to
>>comp.lang.php (amongst others)
>
>
> Not wanting to get away from the main pont, I only posted into two related
> groups. Sometimes it is not clear to which group to post. I do not see why
> it is such a problem cross posting if the groups are carefully selected and
> relevant. Maybe it is the Newsreader I use does not make it a problem, and
> maybe I will now hear otherwise, but what really is the big problem with the
> occasional cross posting on groups that are related. Surely it is better
> then posting the same message twice into each group but at different times.
>
> Kind regards
>
> Dave
>
>

Dave,

I agree this is subverting the normalization process. Why update a
field with this information? Just use your select statement, adding

HAVING count(class_id) = 0;

This will get all the students with no classes.

Otherwise you need to run the update statement before you run the select
- duplicate work.

As to whether to post here or someplace else. This is the wrong place
to post. You have a SQL question, not a PHP question.
comp.databases.mysql would be a much better place to ask this question.



--
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Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
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