Add a default value to a column through a migration

How do I add a default value to a column that already exists through a migration?

All the documentation I can find shows you how to do it if the column doesn't already exist but in this case it does.

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Here's how you should do it:

change_column :users, :admin, :boolean, :default => false

But some databases, like PostgreSQL, will not update the field for rows previously created, so make sure you update the field manaully on the migration too.

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change_column_default :employees, :foreign, false

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For Rails 4+, use change_column_default

  def change
    change_column_default :table, :column, value
  end

Here's a link to change_column_default documentation.

链接地址: http://www.djcxy.com/p/47186.html

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