I used to manage a couple very large MySQL Databases (like, 1TB+). They were huge, unforgiving beasts with an endless appetite to cause me stomach problems. I read everything I could find on MySQL Performance Tuning and innodb. Here’s a summary of what helped me: 1. The book High Performance MySQL is good, but only [...]

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There are 5 different integer columns, each hold integer values of different sizes. Moreover, each can be signed or unsigned. If your value can’t ever be negative (for example, for an index), then you should probably make your values unsigned. DROP TABLE `foo`.`example_03`; CREATE TABLE IF NOT EXISTS `foo`.`example_03` ( f_01 TINYINT, — from -128 [...]

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This example shows how to set default values for each column — as well as how to allow (or not allow) NULL values in the column. By default, any column can contain NULL values. (Note that we’re also using “CREATE TABLE IF NOT EXISTS” so an error doesn’t get thrown if the table already exists [...]

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Here’s a basic example of a MySQL CREATE TABLE command. CREATE TABLE `foo`.`example_01` ( `field_1` VARCHAR(255), `field_2` CHAR(10), `field_3` INT(10), `field_4` BIGINT(20), `field_5` DATETIME ); Notice that the ‘back tic’s on each column definition (the little ` characters) are optional in most cases. I use them for reasons I’ll discuss later on. Also, for most [...]

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Save to delicious. Sometimes when using Active Record you may want to create a database connection to a database other than the default database specified in your database.yml file. When this happens, the easiest way to do it is to use the Class-level convenience method on ActiveRecord::Base. Like this: Imagine your database.yml entry looks like [...]

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(Save this to Del.icio.us!) What is a cursor and when should you use one? A ‘cursor’ in MySQL is essentially just the result set that’s returned from a query. Using a cursor allows you to iterate, or step through, the results of a query and perform certain operations on each row that’s returned. Think of [...]

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