创建默认支持utf8的数据库 createdatabasedb1defaultcharactersetutf8; 命令行 rakedb：***** script/generatemodeltaskname:stringpriority:integer script/generatemigrationadd_description_to_taskdescription:string script/generatemigrationremove_de

创建默认支持utf8的数据库

create database db1 default character set utf8;

命令行
rake db：*****
script/generate model task name:string priority:integer
script/generate migration add_description_to_task description:string
script/generate migration remove_description_from_task description:string

数据类型
引用
# :string, :text, :integer, :float,:decimal, :datetime, :timestamp, :time, :date,
# :binary, :boolean

与db有关的rake任务

db:charset 检索当前环境下数据库的字符设置
db:collation 检索当前环境下数据库的校对
db:create 用config\database.yml中的定义创建当前 RAILS_ENV 项目环境下的数据库
db:create:all 用config\database.yml中的定义创建所有数据库
db:drop 删除当前 RAILS_ENV项目环境中的数据库
db:drop:all 删除所有在 config\database.yml中定义的数据库
db:reset 从db\schema.rb中为当前环境重建数据库（先删后建）.
db:rollback 回滚(清华出版社一本SQLSERVER书的名词[很奇怪为什么不直接用滚回])数据库到前一个版本. 指定回滚到哪一步要用 STEP=n 参数
db:version 检索当前模式下的版本

备份数据库
rake db:backup:create 根据database.yml的信息备份数据库
rake db:backup:destroy 默认删除一天前的备份数据
rake db:backup:rebuild 默认恢复最新的备份数据

注意：这里设置的备份目录是db的backup目录，可以修改

添加索引
引用

add_index :acls, ["action_id","group_id"],:unique=>true
add_index :acls, :action_id

drop all tables 删除全部表
rake db:migrate VERSION=0

指定恢复/删除：
rake db:migrate:down/up VERSION = version_of_migrati

定义数字精确度
t.integer :total_price, :precision=>8,:scale=>2,:default=>0


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rake db:abort_if_pending_migrations # Raises an error if there are pending migrations
rake db:charset # Retrieves the charset for the current environment's database
rake db:collation # Retrieves the collation for the current environment's database
rake db:create # Create the database defined in config/database.yml for the current RAILS_ENV
rake db:create:all # Create all the local databases defined in config/database.yml
rake db:drop # Drops the database for the current RAILS_ENV
rake db:drop:all # Drops all the local databases defined in config/database.yml
rake db:fixtures:identify # Search for a fixture given a LABEL or ID.
rake db:fixtures:load # Load fixtures into the current environment's database.
rake db:migrate # Migrate the database through scripts in db/migrate.
rake db:migrate:down # Runs the "down" for a given migration VERSION.
rake db:migrate:redo # Rollbacks the database one migration and re migrate up.
rake db:migrate:reset # Resets your database using your migrations for the current environment
rake db:migrate:up # Runs the "up" for a given migration VERSION.
rake db:reset # Drops and recreates the database from db/schema.rb for the current environment.
rake db:rollback # Rolls the schema back to the previous version.
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:sessions:clear # Clear the sessions table
rake db:sessions:create # Creates a sessions migration for use with CGI::Session::ActiveRecordStore
rake db:structure:dump # Dump the database structure to a SQL file
rake db:test:clone # Recreate the test database from the current environment's database schema
rake db:test:clone_structure # Recreate the test databases from the development structure
rake db:test:load # Recreate the test database from the current schema.rb
rake db:test:prepare # Check for pending migrations and load the test schema
rake db:test:purge # Empty the test database
rake db:version # Retrieves the current schema version number
rake doc:app # Build the app HTML Files
rake doc:clobber_app # Remove rdoc products
rake doc:clobber_plugins # Remove plugin documentation
rake doc:clobber_rails # Remove rdoc products
rake doc:guides # Generate Rails guides
rake doc:plugins # Generate documentation for all installed plugins
rake doc:rails # Build the rails HTML Files
rake doc:reapp # Force a rebuild of the RDOC files
rake doc:rerails # Force a rebuild of the RDOC files
rake gems # List the gems that this rails application depends on
rake gems:build # Build any native extensions for unpacked gems
rake gems:install # Installs all required gems for this application.
rake gems:refresh_specs # Regenerate gem specifications in correct format.
rake gems:unpack # Unpacks the specified gem into vendor/gems.
rake gems:unpack:dependencies # Unpacks the specified gems and its dependencies into vendor/gems
rake log:clear # Truncates all *.log files in log/ to zero bytes
rake notes # Enumerate all annotations
rake notes:custom # Enumerate a custom annotation, specify with ANNOTATION=WTFHAX
rake notes:fixme # Enumerate all FIXME annotations
rake notes:optimize # Enumerate all OPTIMIZE annotations
rake notes:todo # Enumerate all TODO annotations
rake rails:freeze:edge # Lock to latest Edge Rails, for a specific release use RELEASE=1.2.0
rake rails:freeze:gems # Lock this application to the current gems (by unpacking them into vendor/rails)
rake rails:unfreeze # Unlock this application from freeze of gems or edge and return to a fluid use of system gems
rake rails:update # Update both configs, scripts and public/javascripts from Rails
rake rails:update:configs # Update config/boot.rb from your current rails install
rake rails:update:javascripts # Update your javascripts from your current rails install
rake rails:update:scripts # Add new scripts to the application script/ directory
rake routes # Print out all defined routes in match order, with names.
rake secret # Generate a crytographically secure secret key.
rake stats # Report code statistics (KLOCs, etc) from the application
rake test # Run all unit, functional and integration tests
rake test:benchmark # Run tests for benchmarkdb:test:prepare / Benchmark the performance tests
rake test:functionals # Run tests for functionalsdb:test:prepare / Run the functional tests in test/functional
rake test:integration # Run tests for integrationdb:test:prepare / Run the integration tests in test/integration
rake test:plugins # Run tests for pluginsenvironment / Run the plugin tests in vendor/plugins/*/**/test (or specify with PLUGIN=name)
rake test:profile # Run tests for profiledb:test:prepare / Profile the performance tests
rake test:recent # Run tests for recentdb:test:prepare / Test recent changes
rake test:uncommitted # Run tests for uncommitteddb:test:prepare / Test changes since last checkin (only Subversion and Git)
rake test:units # Run tests for unitsdb:test:prepare / Run the unit tests in test/unit
rake time:zones:all # Displays names of all time zones recognized by the Rails TimeZone class, grouped by offset.
rake time:zones:local # Displays names of time zones recognized by the Rails TimeZone class with the same offset as the system local time
rake time:zones:us # Displays names of US time zones recognized by the Rails TimeZone class, grouped by offset.
rake tmp:cache:clear # Clears all files and directories in tmp/cache
rake tmp:clear # Clear session, cache, and socket files from tmp/
rake tmp:create # Creates tmp directories for sessions, cache, and sockets
rake tmp:pids:clear # Clears all files in tmp/pids
rake tmp:sessions:clear # Clears all files in tmp/sessions
rake tmp:sockets:clear # Clears all files in tmp/sockets