Impossible is nothing

Защитен: Query multiple tables

Публикацията е защитена с парола. За да я видите, моля въведете паролата:

Postgres vs MySQL

Everyday SQL statements



SHOW status where Variable_name like ‘Th%’ or Variable_name like ‘%Connec%’ ;

Check/Repair tables

mysqlcheck -u root -p***** –auto-repair –check –optimize –all-databases


watch -n 0.5 ‘mysql -u root -ppass -e “SHOW FULL PROCESSLIST” | grep Query’


pg_dump -U test arachnid_archiv_test –inserts -h –encoding=utf8 -f pgsql.sql

Dump for full backup with flushing of the log files

–single-transaction –all-databases –delete-master-logs –flush-logs –master-data=2
> backup_sunday_1_PM.sql

Encoding problems

SHOW VARIABLES LIKE ‘character_set_%’;
curl -i

Creating a database

create database re_production DEFAULT CHARACTER SET utf8 DEFAULT COLLATE utf8_general_ci;

Creating a user

GRANT ALL PRIVILEGES ON arachnid_production.* TO ‘payak’@'%’ IDENTIFIED BY ‘payakpassword’ WITH GRANT OPTION;
GRANT ALL PRIVILEGES ON system3_production.* TO ‘payak’@'%’ IDENTIFIED BY ‘payakpassword’ WITH GRANT OPTION;

mysqladmin -u [user] -h localhost -p password ‘[new_password]‘

SQL for a table


mysql tunel to another machine

ssh -N -f -l root -L s1
open port 3307 on the local machine to and login into s1 with root

Replace text

UPDATE script_histories SET cod_script = replace(cod_script,”observer.ArchiveObserver(siteId)”,”observer.ArchiveObserver(siteId, script_id, owned_source_id)”);

Copy from one table to another

DELETE FROM system3_production.articles;
INSERT INTO system3_production.articles SELECT * FROM arachnid_from_screen.articles;

Sessions for Rails

select count(*) from sessions where updated_at < DATE_SUB(now(), INTERVAL 3 DAY);

Binnary loging

Check this attachment here: mysql-presentation on replication etc.


max_allowed_packet = 50M

query_cache_limit=8M #~~~ removed, 1M def. max pozwl. razmer za cache-hirane na edna zajawka
query_cache_size=128M #~~~ 32M, 0 def.

Restoring the maintian Debian User

Archiving data – great article


Full Text search with MySQL

Goodbye MySQL

I was optimistic that I could make, a price monitoring website to use the fulltext search of mysql. Unfortuntly I have found so many drawbacks that I have to leave this idea. The main source for information for me was:

At first the speed was wonderfull. I was searching in 300k> records apx. 350mb. But then I have to surrender. I cant configure mysql to work as I want. I know that If I spend two days to become expert on C/C++ with Unicode I will success but this is not the case. I want working solution.

The resons that make me not to use mysql for searching:

There is no way to change the default operator by default it is OR. You must parse the user query and rewrite it.

I want automaticaly truncation on all my terms.

There is no way to tell MySQL what are characters, and what are not…..sorry, there are two ways:

1. Touching the sources,

2. Configuring in xmls

No documentation on both. Maybe there is …somewhere.

If you use the default configuration then you will wonder how you get or not get the required results.

Here is a summary of the comands that I use to tweak my mysql server:

SET @global.ft_min_word_len=2;
SET @local.ft_min_word_len=2;

But it is better to have those options in my.conf


To check what characterset is using your mysql:

SHOW VARIABLES LIKE ‘character_sets_dir’;

/usr/share/mysql/charsets | E:MySQL Server 5.1sharecharsets

After that you need to rebuild your index with one of those commands
slow: REPAIR TABLE products QUICK;
slow: myisamchk –recover –ft_min_word_len=3 tbl_name.MYI


Database migration from cp1251 -> utf8

It was time to migrate database from cp1251 -> utf8, I have prepared one nice script which will show you step by step the commands that you should run in order to migrate your database.

Copy the content to or use the commands manually

The script is making echo instead of running the commands because this will give you a chance to fix an error if occurs.

As a bonus here is a command with which you can convert an all your html pages to utf8 also

find . -name '*.html' -exec recode -v -f windows-1251..UTF-8 \{\} +

This would recursively find all htmls in the current directory.

How to detect character sets

Migrating Latin1 -> UTF8

We have the mistake to enter all the data in the database (utf8) without setting the right connection encoding (set names utf8). In this case our content is stored as latin1 characters in the utf8 database.

Here is the magic that fixes the encoding found by my bright colleague bl8cki

alter table articles convert to character set latin1;
alter table articles change content content blob;
alter table articles change title title blob;
alter table articles change author author blob;
alter table articles change content content text character set utf8;
alter table articles change title title text character set utf8;
alter table articles change author author text character set utf8;

here is an example

As the example shows it works with cyrilic (pasted in utf8) !