in my db/migrate folder im having many migrations files that
creates tables,add columns,and remove columns.i created a new migration
file now and can i run only this new migration file using rake
command.how to run a specific migration using rake command.people know
it help me please.
You can do:
rake db:migrate VERSION=12
to run the migrations necessary to get to version 12 from wherever you are. If the database is at version 11, that will cause the 012_* up migration to run, if at 13, the 012_* down migration will run. There is no command to pluck a particular migration out of the middle and run it (up or down).
Normally, you just add the migration and run: rake db:migrate
and it does the right thing. I tend to make a backup of the development database and then run migrations forward VERSION=12 and then backward VERSION=11 until I'm sure that the migration is reversible (usually when there's some non-trivial data-munging going on).
Rob Biedenharn http://agileconsultingllc.com
For specific updates you can manipulate the schema.rb file accordingly and load it.
rake db:schema:dump dumps the schema and load does the opposite.
So you can dump, include all the migration changes you want and load for a quick solution.