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35 lines
1.0 KiB
Markdown
35 lines
1.0 KiB
Markdown
# Remove A Database Column From A Table
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The `ActiveRecord` migration DSL includes a method
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[`remove_column`](https://api.rubyonrails.org/v7.0.3.1/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-remove_column)
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that can be used to remove an existing column from a table.
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It can be used like so, to remove the `sign_in_count` column from the `users`
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table.
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```ruby
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def change
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remove_column :users, :sign_in_count
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end
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```
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Though that will work fine, you'll run into an `IrreversibleMigration` error if
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you try to `rails db:rollback`. It usually a good bet to make migrations
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reversible when it is easy to do so.
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All we need in order to make this migration reversible is to add the column
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type.
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```ruby
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def change
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remove_column :users, :sign_in_count, :integer
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end
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```
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Now you can rollback (or [migrate up-down-up](migrating-up-down-up.md)) no
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problem.
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Keep in mind that only the structural changes are reversible. When you remove
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the column, all of the data goes with it, and that cannot be undone with a
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simple rollback.
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