Yesterday, I was on the freenode ##pentaho irc channel when Andres Chaves asked me how to calculate the Nth percentile in MySQL. He saw a solution somewhere using subqueries, but wasn't too happy about it.

A while ago I wrote about calulating the median in MySQL, and it turns out the Nth percentile can be calculated using a similar, single-pass approach, not relying on subqueries, UDFs, or user-defined variables.
The percentile....
So, what is a percentile exactly? Here's what the wikipedia says:

A percentile is the value of a variable below which a certain percent of observations fall. So the 20th percentile is the value (or score) below which 20 …

I haven't received my copy of the book yet, but being unable to control my temptation I have started reading it over Safari while waiting for my own very personal copy. :)

Already a fan of the first edition, you can feel the same charisma being carried over in this book also. The best part of the book is the simplicity by which you are set sailing over MySQL.

Without doubt, it is one of the best books MySQL can ask for. Certainly, I would recommend this book to anyone who is associated with the word MySQL. Or otherwise if you answer yes to any of these questions below, then go and grab a copy.

• Are you a developer working/struggling with MySQL?
• Are you a DBA working/struggling with MySQL?
• Do you intend to learn MySQL?
• Are you fascinated by databases and open-source?
• Do you work with some …

Thankfully my RSS reader has builtin-search capability, so I can quickly skim the full RSS feed from blogs.sun.com for keywords of interest. I found the following articles quite helpful:

• Setting up MySQL Cluster using Solaris Zones by Hashamkha Pathan walks through the steps involved of setting up a virtual MySQL Cluster setup on a single Solaris instance (for evaluation purposes only - this is probably not the best idea for a productive HA environment)
• Mixing SQL and shell commands in MySQL by Amit Saha explains how to write scripts that execute both SQL statements and unix shell commands using the MySQL command line client
• …

Assume you're running MySQL with Innodb tables and you've got crappy hardware, driver bug, kernel bug, unlucky power failure or some rare MySQL bug and some pages in Innodb tablespace got corrupted. In such cases Innodb will typically print something like this:

InnoDB: Database page corruption on disk or a failed
InnoDB: file read of page 7.
InnoDB: You may have to recover from a backup.
080703 23:46:16 InnoDB: Page dump in ascii and hex (16384 bytes):
... A LOT OF HEX AND BINARY DATA...
080703 23:46:16 InnoDB: Page checksum 587461377, prior-to-4.0.14-form checksum 772331632
InnoDB: stored checksum 2287785129, prior-to-4.0.14-form stored checksum 772331632
InnoDB: Page lsn 24 1487506025, low 4 bytes of lsn at page end 1487506025
InnoDB: Page number (if stored to page already) 7,
InnoDB: space id (if created with >= MySQL-4.1.1 and stored already) 6353
InnoDB: Page may …

I finally got the Eclipse debugger to play nicely with MySQL!!!

Steps:
make clean
./configure --with-debug (and I modified my flags with -g as well, tho it's not required)

then under Eclipse I did a 'make all'
used --gdb --one-thread when running
be sure to close the 'registers' pane or else MySQL will crash and require a kill -9

I can now step through my code and see it in action,
it really is doing just what I thought it should!
(tho I found the MySQL GUI tools do a lot of things I didn't know about)

I'll be submitting an early review to my mentor tonight.
I'm not too familiar with submitting a diff so I'll probably attach the full source files as well in case I mess it up.
As of tonight I have surpassed 100 hours working on this project!
In a way I wish all this really was for JUST a t-shirt, adding money to the mix is both …

The PDO SQL parser causes many bugs. All drivers suffer from it. By default the parser replaces placeholder with '<bound_value>'.'<bound_value>' is a string. This can clash with the SQL syntax. PDO can make an INSERT fail. Please learn why and stop reporting bogus bugs.

Why does PDO parse my SQL commands?

PDO has chosen Prepared Statements as its preferred way of running database queries. The entire API is build around prepared statements. Wez has explained that primarily security considerations have caused this decision. Read PDO_MYSQLND: Prepared Statements, again for a discussion of prepared statements in the context of PDO.

Not every database system supports prepared statements. And those who do use a different syntax for placeholder. Some systems support …

The PDO SQL parser causes many bugs. All drivers suffer from it. By default the parser replaces placeholder with '<bound_value>'.'<bound_value>' is a string. This can clash with the SQL syntax. PDO can make an INSERT fail. Please learn why and stop reporting bogus bugs.

Why does PDO parse my SQL commands?

PDO has chosen Prepared Statements as its preferred way of running database queries. The entire API is build around prepared statements. Wez has explained that primarily security considerations have caused this decision. Read PDO_MYSQLND: Prepared Statements, again for a discussion of prepared statements in the context of PDO.

Not every database system supports prepared statements. And those who do use a different syntax for placeholder. Some systems support …

MySQL Proxy is very flexible and can be used for many different use-cases

• Load Balancing
• Failover management
• synchonized Replication
• Caching
• Query Filtering, Rewriting, ...

What shall we implement first, where should our priority ?

Cast you vote at http://dev.mysql.com/tech-resources/quickpolls/

The PDO SQL parser causes many bugs. All drivers suffer from it. By default the parser replaces placeholder with '<bound_value>'.'<bound_value>' is a string. This can clash with the SQL syntax. PDO can make an INSERT fail. Please learn why and stop reporting bogus bugs.

Why does PDO parse my SQL commands?

PDO has chosen Prepared Statements as its preferred way of running database queries. The entire API is build around prepared statements. Wez has explained that primarily security considerations have caused this decision. Read PDO_MYSQLND: Prepared Statements, again for a discussion of prepared statements in the context of PDO.

Not every database system supports prepared statements. And those who do use a different syntax for placeholder. Some systems support …