PJ wrote:
Bob McConnell wrote:
From: PJ
First, let me thank you all for responding and offering suggestions. I
appreciate it and I am learning things.
However, it looks like my message is not getting across:
The problem is not to retrieve only the authors whose last names begin
with A:
Actually, it appears you simply don't like the accurate answers you have
been given.
First, let me say that I am pretty fresh to all this.
Second, I believe I can get the authors with several more queries as I
have done for listings of all the books and by categories, but I am
trying to limit the queries thinking that that will speed up the data
retrieval.
A friend of mine who manages many large scale websites with massive
databases says that isn't always the case, especially if you don't have
a dedicated SQL server with very fast disks and lots of memory.
He's found that in many situations it is faster to do several sql
queries and let php sort it out then to use a bunch of joins,
subselects, etc. in order to reduce the number of sql queries.
Has to do with how sql works on the filesystem, and the IO that can
result from sql needing to do a more complex query, and what is fastest
varies upon your setup. I think he said sub-selects are the worst
because sql has to create a virtual table for the subselect and that can
really slow the query down, but I might be mistaken about that.
Thus unless he has a problem application that is way too slow on
hardware he can't upgrade, he opts for what is easier code to read and
maintain. Sometimes that's faster than hard to read queries anyway.
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