生成User的数据模型后，需要更新数据库使之生效:
[fangpeng@vps1 rails.pureage.info]$ rake db:migrate
== 20150405172157 CreateUsers: migrating ======================================
-- create_table(:users)
-> 0.0014s
== 20150405172157 CreateUsers: migrated (0.0016s) =============================
rake其实是ruby里的类似于Unix的make的工具，经常用在跟数据库相关的任务中。 查看rake有哪些数据库相关的操作，可以使用rake -T db:
[fangpeng@vps1 rails.pureage.info]$ rake -T db
rake db:create # Creates the database from DATABASE_URL or config/database.yml for the current RAILS_EN...
rake db:drop # Drops the database from DATABASE_URL or config/database.yml for the current RAILS_ENV ...
rake db:fixtures:load # Load fixtures into the current environment's database
rake db:migrate # Migrate the database (options: VERSION=x, VERBOSE=false, SCOPE=blog)
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:cache:clear # Clear a db/schema_cache.dump file
rake db:schema:cache:dump # Create a db/schema_cache.dump file
rake db:schema:dump # Create a db/schema.rb file that is portable 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 ...
rake db:structure:dump # Dump the database structure to db/structure.sql
rake db:structure:load # Recreate the databases from the structure.sql file
rake db:version # Retrieves the current schema version number
rake test:all:db # Run tests quickly, but also reset db
rake test:db # Run tests quickly, but also reset db
其中，最常用的就是rake db:migrate.
使用rake -T可以查看所有的任务:
[fangpeng@vps1 rails.pureage.info]$ rake -T
rake about # List versions of all Rails frameworks and the environment
rake assets:clean[keep] # Remove old compiled assets
rake assets:clobber # Remove compiled assets
rake assets:environment # Load asset compile environment
rake assets:precompile # Compile all the assets named in config.assets.precompile
rake cache_digests:dependencies # Lookup first-level dependencies for TEMPLATE (like messages/show or commen...
rake cache_digests:nested_dependencies # Lookup nested dependencies for TEMPLATE (like messages/show or comments/_c...
rake db:create # Creates the database from DATABASE_URL or config/database.yml for the curr...
rake db:drop # Drops the database from DATABASE_URL or config/database.yml for the curren...
rake db:fixtures:load # Load fixtures into the current environment's database
rake db:migrate # Migrate the database (options: VERSION=x, VERBOSE=false, SCOPE=blog)
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:cache:clear # Clear a db/schema_cache.dump file
rake db:schema:cache:dump # Create a db/schema_cache.dump file
rake db:schema:dump # Create a db/schema.rb file that is portable 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 (u...
rake db:structure:dump # Dump the database structure to db/structure.sql
rake db:structure:load # Recreate the databases from the structure.sql file
rake db:version # Retrieves the current schema version number
rake doc:app # Generate docs for the app -- also available doc:rails, doc:guides (options...
rake log:clear # Truncates all *.log files in log/ to zero bytes (specify which logs with L...
rake middleware # Prints out your Rack middleware stack
rake notes # Enumerate all annotations (use notes:optimize, :fixme, :todo for focus)
rake notes:custom # Enumerate a custom annotation, specify with ANNOTATION=CUSTOM
rake rails:template # Applies the template supplied by LOCATION=(/path/to/template) or URL
rake rails:update # Update configs and some other initially generated files (or use just updat...
rake routes # Print out all defined routes in match order, with names
rake secret # Generate a cryptographically secure secret key (this is typically used to ...
rake stats # Report code statistics (KLOCs, etc) from the application or engine
rake test # Runs all tests in test folder
rake test:all # Run tests quickly by merging all types and not resetting db
rake test:all:db # Run tests quickly, but also reset db
rake test:db # Run tests quickly, but also reset db
rake time:zones:all # Displays all time zones, also available: time:zones:us, time:zones:local -...
rake tmp:clear # Clear session, cache, and socket files from tmp/ (narrow w/ tmp:sessions:c...
rake tmp:create # Creates tmp directories for sessions, cache, sockets, and pids