Config database my sql

1. The first
1.  bundle exec rake db:create
2. Then it genrate 3 envirement: development, test, production
3. https://qiita.com/tetsuya/items/f21170a9667d7e465da8 
2. Rake migrate db
   • db:migrate runs (single) migrations that have not run yet.
   • db:create creates the database
   • db:drop deletes the database
   • db:schema:load creates tables and columns within the (existing) database following schema.rb
   • db:setup does db:create, db:schema:load, db:seed
   • db:reset does db:drop, db:setup

   Typically, you would use db:migrate after having made changes to the schema via new migration files (this makes sense only if there is already data in the database). db:schema:load is used when you setup a new instance of your app.
   I hope that helps.
   

   ---

   UPDATE for rails 3.2.12:
   I just checked the source and the dependencies are like this now:
   

   • db:create creates the database for the current env
   • db:create:all creates the databases for all envs
   • db:drop drops the database for the current env
   • db:drop:all drops the databases for all envs
   • db:migrate runs migrations for the current env that have not run yet
   • db:migrate:up runs one specific migration
   • db:migrate:down rolls back one specific migration
   • db:migrate:status shows current migration status
   • db:rollback rolls back the last migration
   • db:forward advances the current schema version to the next one
   • db:seed (only) runs the db/seed.rb file
   • db:schema:load loads the schema into the current env's database
   • db:schema:dump dumps the current env's schema (and seems to create the db as well)
   • db:setup runs db:schema:load, db:seed
   • db:reset runs db:drop db:setup
   • db:migrate:redo runs (db:migrate:down db:migrate:up) or (db:rollback db:migrate) depending on the specified migration
   • db:migrate:reset runs db:drop db:create db:migrate