CODEWITHSUNDEEP
ruby-on-rails
Motombo
Motombo

Reputation: 1787

Duplicate Column name in rails

i'm new to rails and following a tutorial where we created some entries. Currently when I run the server it tells me 

Migrations are pending. To resolve this issue, run: bin/rake db:migrate RAILS_ENV=development

Then I noticed after seeing some SO posts, I should do things like run

rake db:migrate

Then I realized when I did that I got a bunch of lines and one which had this

ActiveRecord::StatementInvalid: SQLite3::SQLException: duplicate column name: description: ALTER TABLE "articles" ADD "description" text

Which I presume the problem comes from. Now i'm not an expert in rails, but how can I identify where this duplicate column is from, when I do 

rails console- > Article.all

I get

    <ActiveRecord::Relation [#<Article id: 1, title: "This is my first article", 

description: "This is the description", created_at: "2016-07-20 00:03:42", 

updated_at: "2016-07-20 00:03:42">, #<Article id: 2, title: "This is an endited

 title", description: "This is my second description", created_at: "2016-07-20 

00:05:39", updated_at: "2016-07-20 00:40:54">]

Which I created yesterday. But where is this duplicate description field? Where should I be looking?

My two migration files look like this by the way

class CreateArticles < ActiveRecord::Migration
  def change
    create_table :articles do |t|
      t.string :title
      t.text :description
      t.timestamps null: false
    end
  end
end

Another

 class AddDescriptionToArticles < ActiveRecord::Migration
      def change
        add_column :articles, :description, :text
        add_column :articles, :created_at, :datetime
        add_column :articles, :updated_at, :datetime
      end
    end

My schema

ActiveRecord::Schema.define(version: 20160715020218) do

  create_table "articles", force: :cascade do |t|
    t.string   "title"
    t.text     "description"
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
  end

end

Upvotes: 0

Views: 2465

Answers (2)

John Hayes-Reed
John Hayes-Reed

Reputation: 1428

The reason you are getting the error saying you have duplicate columns is because you simply are trying to add columns which already exist in your model.

lets run through your first migration file:

class CreateArticles < ActiveRecord::Migration
  def change
    create_table :articles do |t|
      t.string :title
      t.text :description
      t.timestamps null: false
    end
  end
end

In the create_table block you have the following lines: t.string :title <- this creates a title column of type string. t.text :description <- this creates a description column of type text. t.timestamps, null: false <- this creates two columns: created_at and updated_at both of type datetime with the not_null flag on them.

Now in your second migration file you are trying to add three columns:

add_column :articles, :description, :text
add_column :articles, :created_at, :datetime
add_column :articles, :updated_at, :datetime

But as we stated above they have already been created, and therefore are duplicates which can not be made. So the best option to solve your problem would be to just delete this second migration file where you are using add_column and everything should be ok.

Upvotes: 1

Ren
Ren

Reputation: 1374

in the second migration take out the line add_column :articles, :description, :text. You already created a description column when you created the articles table in the first migration, with the line t.text :description:

create_table :articles do |t|
  t.string :title
  t.text :description
  t.timestamps null: false
end

That's the duplicate column Rails is referring to in the error. Next time before you run migrations you can check schema.rb file to see what your database tables look like

Missed this the first time, but you also are duplicating your timestamp columns, created_at and updated_at So the second migration is unnecessary

Upvotes: 1

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