Rails migration for change column

We have script/generate migration add_fieldname_to_tablename fieldname:datatype syntax for adding new columns to a model.

On the same line, do we have a script/generate for changing the datatype of a column? Or should I write SQL directly into my vanilla migration?

I want to change a column from datetime to date .

---

我认为这应该工作。

change_column :table_name, :column_name, :date

---

You can also use a block if you have multiple columns to change within a table.

Example:

change_table :table_name do |t|
  t.change :column_name, :column_type, {options}
end

See the API documentation on the Table class for more details.

---

I'm not aware if you can create a migration from the command line to do all this, but you can create a new migration, then edit the migration to perform this taks.

If tablename is the name of your table, fieldname is the name of your field and you want to change from a datetime to date, you can write a migration to do this.

You can create a new migration with:

rails g migration change_data_type_for_fieldname

Then edit the migration to use change_table:

class ChangeDataTypeForFieldname < ActiveRecord::Migration
  def self.up
    change_table :tablename do |t|
      t.change :fieldname, :date
    end
  end
  def self.down
    change_table :tablename do |t|
      t.change :fieldname, :datetime
    end
  end
end

Then run the migration:

rake db:migrate

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