新手问题 Rails 里面数据库变更操作
做为新手，经常碰到的问题就是数据库建立了，比如 rake db:create 然后也 rake db:migrate 了，然后写着写着发现数据库里面字段不够用了，这个时候要 add column，或者多了要 Remove column，这个时候怎么操作啊？我是 Rails 4. 还有就是常常建立了一个 model 后，migrate 了，删除 model 后，怎么删除对应的 db 呢？有的时候用 rollback 还行，但是如果都操作都好多步了，要回去都不晓得怎么搞了，有好几次都用 drop 把所有数据库都干掉了，所以想请问就是这种情况如何弄呢？请高手指教。
http://guides.rubyonrails.org/migrations.html
rails generate migration AddDetailsToProducts
rake db:migrate VERSION=20080906120000
rake db:drop
rake db:create
rake db:migrate
rake db:seed
rake db:reset # ==前面四条
rake db:setup # rake db:create & rake db:migrate & rake db:seed
看看rake -T
删除的时候也是建 Migration 执行删除动作。 请阅读： http://guides.ruby-china.org/active_record_migrations.html
多试试，手动编辑 migration 文件也是可以的，添加字段rails generate migration AddDetailsToProducts
rake -T | grep db:
rake db:create # Creates the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:c...
rake db:drop # Drops the database from DATABASE_URL or config/database.yml for the current RAILS_ENV (use db:dro...
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 to also dro...
rake db:structure:dump # Dump the database structure to db/structure.sql
rake db:version # Retrieves the current schema version number