Looking at how people are using COUNT(*) and COUNT(col) it looks like most of them think they are synonyms and just using what they happen to like, while there is substantial difference in performance and even query result.

Lets look at the following series of examples:

PLAIN TEXT SQL:

1. CREATE TABLE `fact` (
2.   `i` int(10) UNSIGNED NOT NULL,
3.   `val` int(11) DEFAULT NULL,
4.   `val2` int(10) UNSIGNED NOT NULL,
5.   KEY `i` (`i`)
6. ) ENGINE=MyISAM DEFAULT CHARSET=latin1
7.  
8.  
9. mysql> SELECT count(*) FROM fact;
10. +----------+
11. | count(*) |
12. +----------+
13. |  7340032 |
14. +----------+
15. 1 row IN SET (0.00 sec)
16.  
17.  
18. mysql> SELECT count(val) FROM fact;
…

In two weeks from now, the MySQL Conference & Expo 2007 will take place in Santa Clara, California. Our team has been very busy with working with the conference management team from O'Reilly to prepare for this event, especially Jay who is in charge of organizing and arranging the more than 110 sessions that will be held in several parallel tracks. The conference program looks very exciting, I am impressed by the wide range of topics and quality of speakers that we have lined up.

In addition to the presentations and tutorials, there will also be an Expo, where partner companies will exhibit their products …

It gives us great pride to announce the release of MyComponents V4.5 native Delphi/Kylix VCL suite. This update includes mainly fixes to issues as it has been reported to Support and on this and other forums as well as Delphi 2007 packages, help, apis and demos.

This update is free of charge for all customers whom own a 2005.4.x MyComponents serial. Everyone still using a pre-2005.4 MyComponents may upgrade to the newest version by logging into their Secure accounts: simply click the Secure link at the top of this page.

Previous articles concerning MyComponents 4.x are:
MyComponents 2005.4.4 released
MyComponents 2005.4.3 …

Luhn algorithm can be used on Credit Card number verification stage.
So, probably, it could be usefull for somebody else.
Here is my implementation:

DELIMITER //
CREATE FUNCTION `LuhnCheck` (CC CHAR(19)) RETURNS BOOLEAN
BEGIN
  DECLARE i, mysum, r INT;
  DECLARE skip BOOLEAN;

  SET skip = TRUE;
  SET mysum = 0;

  SET i = CHAR_LENGTH(CC);

  WHILE i > 0 DO
    IF NOT skip THEN
      SET r = SUBSTRING(CC, i, 1) * 2;
      SET mysum = mysum + IF(r > 9, r - 9, r);
    ELSE
      SET mysum = mysum + SUBSTRING(CC, i, 1);
    END IF;

    SET i = i - 1;
    SET skip = NOT skip;
  END WHILE;

RETURN IF((MOD(mysum, 10) = 0) AND mysum <> 0, TRUE, FALSE);
END;
//
DELIMITER ;

More elegant solutions are welcome.

And here it is implemented with PLT Scheme. …

So Jay Pipes pointed out that Eben Moglen is speaking at the upcoming MySQL Conference in his attention grabbing post: Getting Drunk with Eben Moglen.

I saw Eben speak at linux.conf.au 2005 in Canberra - which was totally totally awesome.

I’m really looking forward to seeing him again - honestly, it’s probably worth the conference admission fee just to see this session.

I’ll present a session on the innotop MySQL and InnoDB monitoring tool at 2007 MySQL Conference and Expo in a couple of weeks. The innotop session will focus on using innotop’s basic and intermediate-level features. I’ll demonstrate how to install it and get the initial configuration set up. I’ll show you what innotop is good at doing, and how to do some of the things I do frequently, such as watch queries, check replication status, and look at what transactions are currently open.

As you probably have noticed my blog has been a bit quiet lately. I've
been very busy with some very interesting developments. I've been
working very hard on benchmarking of MySQL Cluster together with
Dolphin and Intel. There will be a lot of material coming out from this
the next couple of weeks. I've prepared a couple of white papers on
how MySQL Cluster can scale to new heights.

I'll have a presentation at the MySQL Users Conference
http://www.mysqlconf.com
where I'll describe all the interesting tidbits of how to tune MySQL
Cluster performance. This will include both choice of HW, use of
configuration parameters, which particular new features to especially
look out for and so forth.

If you want to prepare for this then download the white papers that
will be available from MySQL and from Dolphin
http://dev.mysql.com
…

In about two weeks, I'll by flying to Santa Clara to attend the MySQL Conference. While this is pretty cool by itself, there's more. I won the trip and all expenses are covered by the cool guys at Proven Scaling!

A few weeks ago, they came out with the offer to send three people from around the world to the conference. All you had to do was to describe why you want to go, why they should pick you and what you do. I did that and here I go :-)

Congratulations to Sean Walberg and Carlos Proal Aguilar, the other two winners. See you in California!

This will be my first trip to the West Coast and I'm really looking forward to see how things are in Silicon Valley. Jeremey from Proven Scaling was kind enough to schedule my flights so I could stay a few more days in Santa …

My project has been linked to Digg.

I'm putting together a page of projects which use MySQLdb. If your project is not on this list, leave a comment, with a URL and brief description, and I'll check it out.
Frameworks/Libraries

• Dabo
• Django
• SQLAlchemy
• SQLObject
• Turbogears
• Webware
• Zope

Applications

• …