解决方法
通过发出rake -T,您有以下数据库任务：
rake db:create # Create the database from DATABASE_URL or 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 using DATABASE_URL or 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 rake db:version # Retrieves the current schema version number@H_502_8@所以要发布bundle exec rake db：drop：all,如果要删除所有迁移,并且假设您只想删除迁移,请删除它们并编写新的迁移. @H_502_8@如果您也想改变模型,请使用rails d模型.
