From Stack Overflow:
My table looks like:
| person_id | car_id | miles |
|---|---|---|
| 1 | 1 | 100 |
| 1 | 2 | 200 |
| 2 | 3 | 1000 |
| 2 | 4 | 500 |
I need to total the miles for each person and then average those totals.
This is a good question to demonstrate how to improve MySQL queries using covering indexes.
The query should return a single value, which is SUM(miles)
/ …
You can define a view in MySQL as follows:
CREATE VIEW v AS SELECT
'MySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQL';
The above long string might give trouble reading, but 'MySQLMy..' is 70 characters long. It will work fine, but check out how MySQL stores it (output of SHOW CREATE VIEW):
CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost`
SQL SECURITY DEFINER VIEW `v` AS select
'MySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQL'
AS `MySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQLMySQL`
This is where the trouble starts. If you backup your schema using mysqldump, it will get the above definition, but when you restore it, you'll get the following error:
[Read more]
ERROR 1166 (42000) at line …
Beyond simple basic vitualization, there are added new and interesting layers of management abstractions and features offered that MySQL users will benefit from by understanding. Being aware of how you might use these features in your enterprise may be beneficial in your next architecture design. To assist we explored using those HA, FT, load balancing features in VMware in the context MySQL. So if your interested please check out the mysql whitepaper http://preview.tinyurl.com/y8n9ktq
As always looking for feedback or your experience.
There will be a series of posts to help describe InfiniDB join
behavior to help understand what is possible as join conditions
change.
Join Profiling Topics:
1) Profiling Overview (this post) - Profile a 5 table join
as cardinality changes. Show scalability.
2) Profiling Multi-Join - Explain and measure InfiniDB
Multi-Join (join n tables in 1 scalable operation). Profile
scalability.
3) Profile In vs. Hash Join - Compare In (list)
performanceRead More...
Objectional statements on Oracle-Sun-MySQL. How Google uses Linux. And more.
Follow 451 CAOS Links live @caostheory on Twitter and
Identi.ca
“Tracking the open source news wires, so you don’t have
to.”
Objectional statements
The European Commission communicated its Statement of Objections
to Oracle’s proposed acquisition of Sun Microsystems to those
involved, prompting Oracle to claim the EC has a profound misunderstanding of
database competition and open source, the US DoJ to reiterate its position
that Oracle’s acquisition of Sun is unlikely to be
anticompetitive and an EC spokesperson to explain that concern
over …
It was quite some time since I last blogged. It's not due
to
inactivity. For those of you that have followed my blog
might
have seen earlier blog posts about a new partitioning
feature.
This new partitioning I first blogged about in July 2006
and
that blog is still the 3rd most popular blog of my blogs,
even
when looking at the last months views. The work on this
started
out in 2005 and so it's nice to now get it in a state where
it's
quality is ready for more heavy testing. For those
interested
in partitioning I think this feature will enlarge the number
of
cases where partitioning is applicable. It's now possible
to
partitioning on many more field types and also on multiple
fields
in an efficient manner.
This feature described by WL#3352 has now been pushed …
So Monty now claims that Oracle is MySQL's main competitor. Given that for years MySQL AB has said the exact opposite is kinda odd. They did have a short run in with SAP but that didn't go any where .. well it resulted in MySQL loosing focus, adding tons of barely functioning features which ended up in this entire roadmap debacle we are still suffering through. Anyways the EC has thrown in their hat to stop the deal. Björn seems to share their concerns and so do many others it seems. I still don't get it. This is my attempt at clarifying my point of view and also making sure that people remember the proper terminology (stop using commercial and proprietary as synonyms).
First this all revolves around the assumption that Oracle lets MySQL linger.
Secondly, anyone can provide commercial support …
[Read more]You know how in addition to the main movie you have extras on the DVD. Extra commentary, bloopers, extra scenes, etc? Well welcome the Tyrant extras. With my previous blog posts I was trying to set-up a case for looking at NOSQL tools, and not meant to be a decision making tool. Each solution has pros and cons that will impact how well the technology works for you. Based on some of the comments and questions to the other blogs, I thought I would put together a little more detail into some of the deficiencies and strengths of Tokyo Tyrant.
#1. How durable is Tokyo Tyrant?
Well I went ahead and built a quick script that just inserted data into a TC table ( an id, and a timestamp) and did a kill -9 on the the server in the middle of it.
Insert:
159796,1256131127.17329 …
Hi – I’m Walt Weeks, Engineering Manager at Calpont. We are pleased to announce the availability of the 0.9.5.0-0 release of InfiniDB Community Edition. This is our latest alpha release and is not recommended for production work.
New functionality we’ve added with 0.9.5.0 includes:
The ability to add new columns to existing tables in an online
fashion – something we know Read More...
Hi – I’m Walt Weeks, Engineering Manager at Calpont. We are pleased to announce the availability of the 0.9.5.0-0 release of InfiniDB Community Edition. This is our latest alpha release and is not recommended for production work.
New functionality we’ve added with 0.9.5.0 includes:
The ability to add new columns to existing tables in an online
fashion – something we know Read More...