Directly from the MySql docs: There are three likely causes for this error message. Usually it indicates network connectivity trouble and you should check the condition of your network if...
A MySQL DECIMAL column is used when it is important to preserve exact precision. It takes two parameters, where precision is the total number of digits and scale the...
...a decimal column definition looks like this: t.decimal :amount, :precision => 6, :scale => 2. Issue MySQL prior to 5.6 stored leading zeros (0003.1) and +/- characters (+2.1) within the column. However, it...
...but only have one huge ibdata1 in your /var/lib/mysql and the directories inside your mysql data directory don't represent the actual database sizes? This is for you!
...a mysql root console: SELECT table_schema AS "Database name", SUM(data_length + index_length) / 1024 / 1024 AS "Size (MB)" FROM information_schema.TABLES GROUP BY table_schema; This will get you...
MySQL version 5.1 comes with an alternative, faster InnoDB implementation (called "InnoDB Plugin"). Switching is easy: Stop your mysqld with sudo stop mysql Add the following lines to your /etc/mysql/my.cnf...
...under the [mysqld] section ignore-builtin-innodb plugin-load=innodb=ha_innodb_plugin.so Start your mysqld with sudo start mysql The file format has not changed, your tables should survive this.
This will make MySQL log all received queries so you can see for yourself what happens on the database level. Don't switch this on for production machines!
sudo vim /etc/mysql/my.cnf In the [mysqld] section, add: log=/var/log/mysql.log Restart your MySQL daemon. On Ubuntu: sudo service mysql restart Note that your MySQL performance will suffer. But when...
This Perl script will run diagnostics on your MySQL database and recommend changes to your MySQL configuration...
...data. Dumping single tables makes sense if a complete dump would be to big. mysqldump -u deploy_user -p application_production table1 table2 table2 > table1_table2_table2.sql.dump Hint: If a table has...
Further reading: How to load only a subset of a massive MySQL dump How to import production database dump to staging (or the other way...
When you do a script/dbconsole -p, your MySQL shell will already be using UTF-8. When you call it yourself using mysql, it may not be enabled.
...of Hlavní město Praha. You need to manually switch on UTF-8, in the MySQL console: SET NAMES 'utf8...
Possible Reason 1: parallel_tests - running more processes than features If you run old versions of parallel_tests with more...
...or end of a word: note.title =~ /\bfoo\b/ Unfortunately \b is not available in MySQL. You can use [[:<:]] and [[:>:]] to match the beginning and end of a word instead:
...FROM notes WHERE title REGEXP "[[:<:]]foo[[:>:]]" These markers are unique to MySQL and not available in Ruby regular expressions...
MMM (MySQL Master-Master Replication Manager) is a set of flexible scripts to perform monitoring/failover and management of MySQL Master-Master replication configurations (with only one node writable at any...
MySQL's MIN and MAX functions are for aggregations only. This will not work and produce an error: SELECT id, MIN(birthday, '1978-01-01') FROM users;
Occasionally some complex query must be processed on the database because building thousands of Ruby objects is impracticable.
...to delete rows from a table, and the delete conditions require a joined table, MySQL needs to know which table you want to delete from. Let's say that Post...
Use this MySQL command to show further info about a table: SHOW CREATE TABLE tags; This will output a table schema like this: CREATE TABLE `tags` ( `id` int(11) NOT...
Usually our mysql queries are not case sensitive. In order to query case sensitive, you can use the mysql COLLATE clause. The collate clause lets you specify a collation, which...
You will occasionally need to clean out your database while keeping the schema intact, e.g. when someone inserted data in...
If you need to export data from MySQL to a CSV, you can profit from really fast built-in methods. This query writes the data to /tmp/geodb_coodinates.csv. And it's...
...month / 3.0).ceil #=> 1 Yes, you do actually divide by 3.0, not 4.0. MySQL has SELECT QUARTER...
In order to open a MySQL shell without the need to enter user and password, you can say the following in any Rails 2 project: script/dbconsole -p
This might be due to AppArmor denying the MySQL server access to most of the filesystem. You can instead use LOAD DATA LOCAL INFILE ... to pipe data through the MySQL...
If you need to do calculations inside the database and can not use Ruby objects you may run into problems...
Unless you changed the default, this will be 16 MB: mysql> SHOW VARIABLES WHERE Variable_name="max_allowed_packet"; +--------------------+----------+ | Variable_name | Value | +--------------------+----------+ | max_allowed_packet...
To clear the query cache in your MySQL database manually, e.g. for database profiling, execute the following command in your MySQL console: RESET QUERY CACHE...