Ruby on rails How to remove added columns and insert new columns through a migration file -


hi created ruby on rails migration file follows , in first stage created tables

then want add columns , remove columns , modified follows 

class createmt940batches < activerecord::migration   def change     create_table :mt940_batches |t|      t.string :account_number      t.string :transaction_reference_number      t.string :information_to_account_owner      t.string :file_name      t.binary :raw_data_transaction      t.string :sha1_checksum      t.timestamps    end     def self.down      remove_column :account_number, :transaction_reference_number, :information_to_account_owner    end     def self.up      add_column :mt940_batches, :created_by, :updated_by, :integer    end   end   end

but when ran rake db:migrate nothing has happens. how accomplish task . want change model created migration file. um looking way this. thank in advance

you should add remove / add column in separate migration file.

class foomigration < activerecord::migration   def down     remove_column :account_number, :transaction_reference_number, :information_to_account_owner   end    def     add_column :mt940_batches, :created_by, :updated_by, :integer   end  end

please note up , down method should idem potent. should able go 1 other when calling rake db:migrate:down , rake db:migrate:up. not case here.

however here, seems want achieve 2 different things in single migration. if want add , remove columns, consider moving each 1 in different migration file:

please read here more details

you end 2 migrations file this:

class removefieldsfrommt940batches < activerecord::migration   def change     remove_column :mt940_batches, :account_number, :transaction_reference_number, :information_to_account_owner   end end  class addfieldstomt940batches < activerecord::migration   def change     add_column :mt940_batches, :created_by, :updated_by, :integer   end end

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