[plug] Optimise MySQL query

[Bernd Felsche]

"James L. Clarke" <jamesc at global.net.au> writes:

>Knowing how to write SQL queries is one of the most useful skills
>you can aquire if you are doing any type of programming that
>requires interaction with a relational databases. Although each
>different database has special things it can do with SQL, most
>databases support the ANSI Stardard SQL, so learning that would be
>your first step.

More importantly, you should first learn about RDBMS. Codd and Date.

Start:
	http://en.wikipedia.org/wiki/Codd's_12_rules

If you know the rules and appreciate why they are, then most
database structures and their applications software look very
depressing.

Once you understand normalisation,. most real-life applications look
definitively evil.

>P.S. I know some people on the Linux group will debate whether
>Access is a relational database. For less than five users (ie small
>business) it is fine as long spilt the code and data it two
>seperate files and you design the thing properly, for more than
>five users you can still use the access for the application but put
>the data in SQL Server, Oracle, DB2 or MySQL. I guess the reason it
>has such a bad rap is that because it is cheep so many people who
>don't really know what they are doing have used it and made a mess.
>However the same could be said of MySQL now-a-days.

Access is *useless* if you have more than a few thousand records.

It is painfully slow. I was able to write an application using *nix
utilities in a shell program that worked faster and more reliably.
And it took me less time to write the shell-based application than
it took to load the data into Access.

I later converted the shell programs and data into an application
built on a proprietary (Progress) database.

Access gives you NO transaction control. I found no way to persuade
it to index data. There is no locking. Data can change while you're
trying to change it if you've foolishly allowed others access to the
same files.

There is no crash recovery. If you're writing to the database when
the machine wedges or power goes off, your database has a high
probability of being screwed.

Some people foolishly share their access database files over the
network. That is bad in a great number of ways.

I will not hesitate to recommend against the use of Access for any
serious work. I don't even use it for trivial stuff.
-- 
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