Rake db:migrate error, table already exists

Question

I accidentally create a migration which I did not need so I delete the file, and created a new migration now when I try to run rake db:migrate I keep getting this error. I am the using SQlite3 gem, and Ruby on Rails 4

StandardError: An error has occurred, this and all later migrations canceled:
SQLite3::SQLException: table "categories" already exists: CREATE TABLE "categories" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "category_name" varchar, "created_at" datetime NOT NULL, "updated_at" datetime NO
T NULL) D:/muse/db/migrate/20150830113519_create_categories.rb:3:in `change'
D:in `migrate'
ActiveRecord::StatementInvalid: SQLite3::SQLException: table "categories" already exists: CREATE TABLE "categories" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "category_name" varchar, "created_at" datetime NO
T NULL, "updated_at" datetime NOT NULL)
D:/muse/db/migrate/20150830113519_create_categories.rb:3:in `change'
D:in `migrate'
SQLite3::SQLException: table "categories" already exists
D:/muse/db/migrate/20150830113519_create_categories.rb:3:in `change'
D:in `migrate'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

Answer 1

This is ocurried with me because I'm trying to do some samples in diferents branchs. So I do this and works:

rake db:drop
rake db:reset or rake db:setup

Answer 2

When you create a migration and run it, and want to make chances, you must first rollback:

$ bin/rake db:rollback STEP=1

At this stage you can delete the file or modify it and run again the migration_

$ bin/rake db:migrate

Now that you deleted the file, you cant rollback. What you have to do is delete the table manually or create a migration to drop that table:

$ bin/rails generate migration DropCategoriesTable

This will generate a migration file. Edit it:

class DropCategoriesTable < ActiveRecord::Migration
  def up
    drop_table :categories
  end

  def down
    raise ActiveRecord::IrreversibleMigration
  end
end

Answer 3

Are you trying to completely remove the table? If so, simply deleting the migration file does not get rid of it as it's already been migrated to your database. If you are trying to change or drop the table, you will need to start a new migration and use "ALTER TABLE". I would recommend checking out this stackoverflow link: How to delete or add column in SQLITE? .