| Re: Loop through array, change headings [message #184450 is a reply to message #184438] |
Wed, 01 January 2014 17:01   |
Arno Welzel
Messages: 317
Registered: October 2011
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Senior Member |
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Am 01.01.2014 01:19, schrieb richard:
> On Tue, 31 Dec 2013 23:00:32 +0000 (UTC), Denis McMahon wrote:
>
[...]
>> Here's one example of why Adriennes approach is easier:
>>
>> Supposing Adrienne decides to rename one of the three classifications. In
>> Adriennes database, that involves a single sql operation on one row in
>> one table. In your hypothetical and seriously fucked up database design,
>> you would need to test each row in the whole database to see if the
>> category was the one that needed to be changed, and then change it. Such
>> a process is highly inefficient in terms of both cpu effort, memory
>> management and disk io, and it is to prevent such inefficiencies amongst
>> other things that relational database design theory has evolved to where
>> it is today.
>>
>> Unlike your comprehension of computer systems which appears to have
>> started at nothing and continues to devolve backwards.
>
> I was merely suggesting one possible way.
> I have never liked the idea of making two tables where one is sufficient.
One table is NOT SUFFICIENT!
Because then EVERY classification has to be repeated over and over again
in every single record.
> In the OP's example, we have going on exactly what you speak of.
No we don't!
> Let's say he wants to add on a second pet shop
> Now he has to change the id's in two tables.
No! "Store" is a CATEGORY and "pet shop" is just an entry. One would
just create a record "Pet shop 2" with the CATEGORY "Store".
> Plus, the remaining id's all have to be changed accordingly.
> So what if he has 1,000 rows?
Even if the CATEGORY of existing entries would have to be changed - this
would be a simple SQL statement.
> He made a change on row 5. So now the sequence of events has to change
> 1990+ items?
No. You don't understand - as usual :-(
--
Arno Welzel
http://arnowelzel.de
http://de-rec-fahrrad.de
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