Rails DB Migration – How To Drop a Table?

Question

I added a table that I thought I was going to need, but now no longer plan on using it. How should I remove that table?

I’ve already run migrations, so the table is in my database. I figure rails generate migration should be able to handle this, but I haven’t figured out how yet.

I’ve tried:

rails generate migration drop_tablename

but that just generated an empty migration.

What is the “official” way to drop a table in Rails?

Since rails generate migration has command-line options for generating migration code for creating tables, adding or changing columns, etc., it would be nice if it also had an option for dropping a table — but it doesn’t. Sure, writing the up part is simple — just call drop_table — but the down part, generating the table again, might not always be so simple, especially if the schema of the table in question has been changed by migrations after its initial creation. Maybe someone should suggest to the developers of Rails that adding such an option would be a good idea. — Teemu Leisti
@TeemuLeisti How about just copy and paste the current table definition from schema.rb? I do it this way all the time… — jasoares
@João Soares: OK, I guess that works. However, it would be nice if the process could be automated, so that you could just give a rake migration-creation command, with the name of a table as a parameter, that would produce the needed up and down functions. — Teemu Leisti

Joe Kennedy · Accepted Answer · 2010-10-26T01:54:46

You won’t always be able to simply generate the migration to already have the code you want. You can create an empty migration and then populate it with the code you need.

You can find information about how to accomplish different tasks in a migration here:

http://api.rubyonrails.org/classes/ActiveRecord/Migration.html

More specifically, you can see how to drop a table using the following approach:

drop_table :table_name

This worked for me too. But on full migrations (installing from scratch) the table will now be first created and later on dropped again. Is it safe to remove the create and drop migrations down the road? — berkes
Any view here on whether it’s better to drop tables or revert to a previous database schema? — william tell
If you’re done with the table and do not plan to use it anymore, I’d say just drop it. Better to get rid of it if its not being used. — Pete
answer by @BederAcostaBorges is more self-explanatory and accurate — onerinas
How to also remove all foreign keys? There are columns in other tables pointing to the table being dropped. — Martin Konicek

Brandon O’Rourke · Accepted Answer · 2011-10-15T18:57:14

First generate an empty migration with any name you’d like. It’s important to do it this way since it creates the appropriate date.

rails generate migration DropProductsTable

This will generate a .rb file in /db/migrate/ like 20111015185025_drop_products_table.rb

Now edit that file to look like this:

class DropProductsTable < ActiveRecord::Migration
  def up
    drop_table :products
  end

  def down
    raise ActiveRecord::IrreversibleMigration
  end
end

The only thing I added was drop_table :products and raise ActiveRecord::IrreversibleMigration.

Then run rake db:migrate and it’ll drop the table for you.

A down migration should be used to recreate the table being dropped. — fflyer05
This migration could never be rolled back, even in development. Would it be better to just leave the down migration blank? — mhriess
@mjnissim and fflyer05 are correct, in order to avoid any weird thing you should recreate the table in the down method. — Sebastialonso
Dropping a table deletes all the data, if you recreate it in the down method you won’t recover it so it’s not actually a proper roll back. It’s better to clearly indicate that the migration is irreversible than to give a false sense that it can be recovered from. — vivi

Beder Acosta Borges · Accepted Answer · 2015-07-27T15:25:02

Write your migration manually. E.g. run rails g migration DropUsers.

As for the code of the migration I’m just gonna quote Maxwell Holder’s post Rails Migration Checklist

BAD – running `rake db:migrate` and then `rake db:rollback` will fail

class DropUsers < ActiveRecord::Migration
  def change
    drop_table :users
  end
end

GOOD – reveals intent that migration should not be reversible

class DropUsers < ActiveRecord::Migration
  def up
    drop_table :users
  end

  def down
    fail ActiveRecord::IrreversibleMigration
  end
end

BETTER – is actually reversible

class DropUsers < ActiveRecord::Migration
  def change
    drop_table :users do |t|
      t.string :email, null: false
      t.timestamps null: false
    end
  end
end

If you’re cutting and pasting into the block from schema.rb, don’t forget to also search schema.rb for foreign keys. Then add the foreign key definition to the drop_table block, e.g.: t.foreign_key "other_table" — Lencho Reyes
I used the 3rd option and it worked perfectly fine for me. Thank you. — Promise Preston

lllllll · Accepted Answer · 2012-11-08T22:38:02

Warning: Do this at your own risk, as @z-atef and @nzifnab correctly point out, Rails will not be aware of these changes, your migration sequence fill fail and your schema will be different from your coworkers’. This is meant as a resource for locally tinkering with development only.

While the answers provided here work properly, I wanted something a bit more ‘straightforward’, I found it here: link
First enter rails console:

$rails console

Then just type:

ActiveRecord::Migration.drop_table(:table_name)

And done, worked for me!

The model is still there until you run rails destroy model User — gm2008
Only run this if you want to get rid of the table for good. Rails will be unaware of this drop. Migration is broken after running this command. Can not CREATE, DROP…ETC. ERROR SQLite3::SQLException: no such table: accruals: DROP TABLE “sometable” — z atef
WARNING: DO NOT DO THIS. You should never ever perform DDL operations on your database straight from the console. Your structure file will have no idea this change was made, your coworkers development environments will be different from your own and from production, it’s just a mess. Use migrations. — nzifnab

Shahzad Tariq · Accepted Answer · 2015-05-26T07:42:53

You need to to create a new migration file using following command

rails generate migration drop_table_xyz

and write drop_table code in newly generated migration file (db/migration/xxxxxxx_drop_table_xyz) like

drop_table :tablename

Or if you wanted to drop table without migration, simply open rails console by

$ rails c

and execute following command

ActiveRecord::Base.connection.execute("drop table table_name")

or you can use more simplified command

ActiveRecord::Migration.drop_table(:table_name)

ssarabando · Accepted Answer · 2015-07-31T14:20:13

rails g migration drop_users
edit the migration

    class DropUsers < ActiveRecord::Migration
      def change
        drop_table :users do |t|
          t.string :name
          t.timestamps
        end
      end
    end

rake db:migrate

Mahesh Mesta · Accepted Answer · 2017-07-28T06:57:26

The simple and official way would be this:

  rails g migration drop_tablename

Now go to your db/migrate and look for your file which contains the drop_tablename as the filename and edit it to this.

    def change
      drop_table :table_name
    end

Then you need to run

    rake db:migrate

on your console.

Srikanth V · Accepted Answer · 2018-12-11T12:26:58

I wasn’t able to make it work with migration script so I went ahead with this solution. Enter rails console using the terminal:

rails c

Type

ActiveRecord::Migration.drop_table(:tablename)

It works well for me. This will remove the previous table. Don’t forget to run

rails db:migrate

Francis Potter · Accepted Answer · 2011-04-03T22:50:40

I think, to be completely “official”, you would need to create a new migration, and put drop_table in self.up. The self.down method should then contain all the code to recreate the table in full. Presumably that code could just be taken from schema.rb at the time you create the migration.

It seems a little odd, to put in code to create a table you know you aren’t going to need anymore, but that would keep all the migration code complete and “official”, right?

I just did this for a table I needed to drop, but honestly didn’t test the “down” and not sure why I would.

Strange but it looks like I’m going to have to do this too. — digitalWestie
Or you can just use: raise ActiveRecord::IrreversibleMigration in the self.down method, so you at LEAST give yourself an error / notice if you ever try to rollback. — Steph Rose
I would test the down just because otherwise I’m introducing untested code into my project. How can I reuse the original migration’s up method? I’ve tried CreateMyTable.up and ActiveRecord::Migrator.run(:up, ActiveRecord::Migrator.migrations_paths, X) where X is the migration that originally created the table, but neither works–in both approaches, AR first checks whether the migration has already been applied, and silently skips it if it has. ` — Isaac Betesh

farz bhullar · Accepted Answer · 2015-10-16T06:59:32

you can simply drop a table from rails console.
first open the console

$ rails c

then paste this command in console

ActiveRecord::Migration.drop_table(:table_name)

replace table_name with the table you want to delete.

you can also drop table directly from the terminal. just enter in the root directory of your application and run this command

$ rails runner "Util::Table.clobber 'table_name'"

shivam · Accepted Answer · 2017-11-20T16:15:28

Alternative to raising exception or attempting to recreate a now empty table – while still enabling migration rollback, redo etc –

def change
  drop_table(:users, force: true) if ActiveRecord::Base.connection.tables.include?('users')
end

Sidney · Accepted Answer · 2017-05-05T17:42:34

You can roll back a migration the way it is in the guide:

http://guides.rubyonrails.org/active_record_migrations.html#reverting-previous-migrations

Generate a migration:

rails generate migration revert_create_tablename

Write the migration:

require_relative '20121212123456_create_tablename'

class RevertCreateTablename < ActiveRecord::Migration[5.0]
  def change
    revert CreateTablename    
  end
end

This way you can also rollback and can use to revert any migration

Mike H-R · Accepted Answer · 2012-12-14T06:41:05

Open you rails console

ActiveRecord::Base.connection.execute("drop table table_name")

Dorian · Accepted Answer · 2014-09-08T22:16:08

ActiveRecord::Base.connection.drop_table :table_name

Dorian

nhegroj

1

If you are working in a development environment this is a much easier solution than answers with more votes
– Kai Durai

Shan · Accepted Answer · 2019-07-18T06:58:05

if anybody is looking for how to do it in SQL.

type rails dbconsole from terminal

enter password

In console do

USE db_name;

DROP TABLE table_name;

exit

Please dont forget to remove the migration file and table structure from schema

icedwater · Accepted Answer · 2013-02-13T20:55:07

I needed to delete our migration scripts along with the tables themselves …

class Util::Table < ActiveRecord::Migration

 def self.clobber(table_name)   
    # drop the table
    if ActiveRecord::Base.connection.table_exists? table_name
      puts "n== " + table_name.upcase.cyan + " ! " 
           << Time.now.strftime("%H:%M:%S").yellow
      drop_table table_name 
    end

    # locate any existing migrations for a table and delete them
    base_folder = File.join(Rails.root.to_s, 'db', 'migrate')
    Dir[File.join(base_folder, '**', '*.rb')].each do |file|
      if file =~ /create_#{table_name}.rb/
        puts "== deleting migration: " + file.cyan + " ! "
             << Time.now.strftime("%H:%M:%S").yellow
        FileUtils.rm_rf(file)
        break
      end
    end
  end

  def self.clobber_all
    # delete every table in the db, along with every corresponding migration 
    ActiveRecord::Base.connection.tables.each {|t| clobber t}
  end

end

from terminal window run:

$ rails runner "Util::Table.clobber 'your_table_name'"

or

$ rails runner "Util::Table.clobber_all"

Anoob K Bava · Accepted Answer · 2015-09-14T12:52:03

the best way you can do is

rails g migration Drop_table_Users

then do the following

rake db:migrate

venkatvb · Accepted Answer · 2015-08-03T12:00:33

Run

rake db:migrate:down VERSION=<version>

Where <version> is the version number of your migration file you want to revert.

Example:-

rake db:migrate:down VERSION=3846656238

shilovk · Accepted Answer · 2021-11-10T18:04:38

Helpful documentation

In migration you can drop table by:

drop_table(table_name, **options)

options:

:force
Set to :cascade to drop dependent objects as well. Defaults to false

:if_exists
Set to true to only drop the table if it exists. Defaults to false

Example:

Create migration for drop table, for example we are want to drop User table

rails g migration DropUsers

Running via Spring preloader in process 13189
   invoke  active_record
   create    db/migrate/20211110174028_drop_users.rb

Edit migration file, in our case it is db/migrate/20211110174028_drop_users.rb

class DropUsers < ActiveRecord::Migration[6.1]
  def change
    drop_table :users, if_exist: true
  end
end

Run migration for dropping User table

rails db:migrate

== 20211110174028 DropUsers: migrating ===============================
-- drop_table(:users, {:if_exist=>true})
   -> 0.4607s

Sarvar Khalimov · Accepted Answer · 2021-11-13T08:22:42

You can’t simply run drop_table :table_name, instead you can create an empty migration by running:
rails g migration DropInstalls

You can then add this into that empty migration:

class DropInstalls < ActiveRecord::Migration
  def change
    drop_table :installs
  end
end

Then run rails db:migrate in the command line which should remove the Installs table
The solution was found here

Let me know if you have any q’s, will try to answer asap
– Sarvar Khalimov — Sarvar Khalimov

Pankaj Dhote · Accepted Answer · 2018-04-20T14:54:46

Drop Table/Migration

run:-
$ rails generate migration DropTablename

exp:- $ rails generate migration DropProducts

Nicollas · Accepted Answer · 2018-06-02T22:17:17

if you want to drop a specific table you can do

$ rails db:migrate:up VERSION=[Here you can insert timestamp of table]

otherwise if you want to drop all your database you can do

$rails db:drop

Dov Benyomin Sohacheski · Accepted Answer · 2016-06-17T13:21:47

Run this command:-

rails g migration drop_table_name

then:

rake db:migrate

or if you are using MySql database then:

login with database
show databases;
show tables;
drop table_name;

Dov Benyomin Sohacheski

Nitin Rakesh

4

Does this answer add anything to the existing, accepted answer? If not, there’s no need to post this.
– Tom Lord
this creates an empty migration in rails 4.2, as already stated in the question itself.
– bert bruynooghe
This is EXACTLY what the OP originally tried…this answer should be removed
– webaholik
Adding a simple answer does not deserve to be downvoted. It still is relevant, I guess. Be kind to newer users please.
– ARK

Suraj Rao · Accepted Answer · 2019-03-04T12:42:03

If you want to delete the table from the schema perform below operation —

rails db:rollback

Suraj Rao

iamnair

1

This command will only undo the last migrate command. If that command is the creation of the table, it will drop the table. But unless you then delete the migration file that creates it, it will be recreated the at the next db:migrate. Keeping your migrations in order to replicate elsewhere is important, especially if work has been done in the meantime. Using db:rollback to change the final database layout is almost guaranteed to ruin many people’s work.
– Sean Hogge

24 Answers
24

BAD – running `rake db:migrate` and then `rake db:rollback` will fail

GOOD – reveals intent that migration should not be reversible

BETTER – is actually reversible

What does MethodImplOptions.Synchronized do?

Pie charts in R leaflet, turn count into sum and ...

Why am I getting "Object is possibly 'undefined'" in this ...

Express JS How to push object to an array of ...

How to initialize standalone Radio Button Group component checked property ...

Sign Up

Sign In

Rails DB Migration – How To Drop a Table?

24 Answers 24

BAD – running rake db:migrate and then rake db:rollback will fail

GOOD – reveals intent that migration should not be reversible

BETTER – is actually reversible

24 Answers
24

BAD – running `rake db:migrate` and then `rake db:rollback` will fail