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copied!<p>You can use <code>rake -T</code> to get the description of each task:</p> <pre><code>$ rake -T | grep db rake db:create # Create the database from config/database.yml for the current Rails.env (use db:create:all to create all dbs in the config) rake db:drop # Drops the database for the current Rails.env (use db:drop:all to drop all databases) rake db:fixtures:load # Load fixtures into the current environment's database. rake db:migrate # Migrate the database (options: VERSION=x, VERBOSE=false). rake db:migrate:status # Display status of migrations rake db:rollback # Rolls the schema back to the previous version (specify steps w/ STEP=n). rake db:schema:dump # Create a db/schema.rb file that can be portably used against any DB supported by AR rake db:schema:load # Load a schema.rb file into the database rake db:seed # Load the seed data from db/seeds.rb rake db:setup # Create the database, load the schema, and initialize with the seed data (use db:reset to also drop the db first) rake db:structure:dump # Dump the database structure to db/structure.sql. Specify another file with DB_STRUCTURE=db/my_structure.sql rake db:version # Retrieves the current schema version number </code></pre> <p>I this what you were asking about?</p> <p><strong>EDIT:</strong></p> <p>You can read more about what migrations are for here: <a href="http://guides.rubyonrails.org/migrations.html" rel="nofollow">http://guides.rubyonrails.org/migrations.html</a></p> <p><strong>EDIT 2:</strong></p> <p><code>rake db:migrate</code> allows you to update the DB schema in a "sane" way: you can create a new migration (read the guides!) and add a new column for example, add an index, rename a column, etc. - migrations allow you to "travel" back and forth in "time" - you can run the migration and rollback it later.</p> <p>When you generate a new migration:</p> <p><code>$ rails g migration add_new_column_to_some_table</code> you will be able to run <code>rake db:migrate</code> later on to apply to changes you want (of course you have to write the body of this generated migration).</p> <p>I STRONLY advise you to read the guides though :)</p> <p><strong>EDIT 3:</strong></p> <p><code>add_column :users, :price, :float</code>, for example, will add <code>price</code> column to the <code>users</code> table, the type of the column will be <code>float</code> (<code>float</code> isn't a best idea to store money related things BTW!). This column will be <code>NULL</code> by default.</p> <p><strong>EDIT 4:</strong></p> <p>Information about which migrations were run is stored in <code>schema_migrations</code> table: running migration for the first time will add a new record in this table with <code>version</code> of this migration (date + some random numbers from the name of the file). Rollbacking a migration will remove this record. Running a migration twice will not have any effect.</p>

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