how am i able to add a column to my books table in rails? i want to do this through a migration
This is my schema:
ActiveRecord::Schema.define(version: 20160716030811) do
create_table "books", force: :cascade do |t|
t.string "name"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
end
You do this by running a migration. It depends on what column you want to add. I see you have a name column already, so if you were to create a description column, run rails generate migration AddDescriptionToBooks description:string
If you want to create a different column just replace the 2 description words in that migration code with whatever you want
This will create a migration which adds a column description to the table.
Related
I am trying to add a new column active to my table students.
I ran rails g migration add_active_to_students active:boolean to generate this migration:
class AddActiveToStudents < ActiveRecord::Migration[5.0]
def change
add_column :students, :active, :boolean, default: true
end
end
But when I run rails db:migrate I get this error:
PG::DuplicateColumn: ERROR: column "active" of relation "students" already exists
: ALTER TABLE "students" ADD "active" boolean DEFAULT 't'`
As you can see there is not actually an active column in students:
create_table "students", force: :cascade do |t|
t.integer "club_id"
t.string "email"
t.string "address_line_1"
t.string "address_line_2"
t.string "city"
t.string "state"
t.integer "postcode"
t.string "phone1"
t.string "phone2"
t.string "first_name"
t.string "last_name"
t.date "dob"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.string "picture"
t.integer "payment_plan_id"
t.string "parent1"
t.string "parent2"
t.string "size"
t.text "notes"
t.index ["club_id"], name: "index_students_on_club_id", using: :btree
end
So why would I be getting this error?
I followed the steps that #demir posted and found that, yes, the column was in the database without being listed in the schema. ALTER TABLE students DROP COLUMN active did not give an error message however it also didn't remove the column.
In the end I removed it by:
Entering the console
rails console
Deleting the column
ActiveRecord::Base.connection.remove_column :students, :active
You may have added it somehow. Have you checked the PG database? Connect to the application database and see if there is an active field.
List databases
\l
Connect database
\c your_app_database_name
List table columns
\d+ students
Check active field, remove it if exist.
ALTER TABLE students DROP COLUMN active
You have this column in your DB, but it wasn't dumped to your schema.rb. Maybe a migration was stopped after it added the column, but before it wrote to schema.rb?
You can remove this column manually, running rails dbconsole and then:
ALTER TABLE students DROP COLUMN active
You can follow the above solutions i.e. drop the column from DB first and then run the migration. Most probably what has happened is, you created and run some migration but later deleted that migration file without doing a db:rollback.
One more option that you can consider is to put a conditional migration like:
class AddActiveToStudents < ActiveRecord::Migration[5.0]
def change
unless column_exists? :students, :active
add_column :students, :active, :boolean, default: true
end
end
end
When I run rails db:migrate without a new migration it seems to have added two new tables: questions and questions_1.
In my schema file I see:
create_table "questions", id: false, force: :cascade do |t|
t.integer "id"
t.text "text"
t.boolean "active"
t.integer "organization_id"
t.datetime "created_at"
t.datetime "updated_at"
t.bigint "account_id"
t.bigint "team_id"
end
create_table "questions_1", id: false, force: :cascade do |t|
t.integer "id"
t.text "text"
t.boolean "active"
t.integer "organization_id"
t.datetime "created_at"
t.datetime "updated_at"
t.bigint "account_id"
t.bigint "team_id"
end
I don't have any migrations making these tables. I'm guessing this is some sort of convention. Where do I look to fix this? All recent changes are in the app/ directory and a migration I made has been rolled back and then deleted. Yet when I run rails db:migrate I always get these new tables.
Any ideas?
Rails won't create tables with any name other than the ones specified in a migration. If the table already exists then it will throw an error.
I believe someone has run a migration creating the second table on your database, and then deleted the migration. When rails creates your schema.rb file, it uses your database rather than any migrations, meaning this file reflects your actual database state rather than the one your migrations suggest would be the case.
If you're sure you don't want the second table and it has no data in it, then you can write out a new migration to delete this table, run it, and then delete it. This will return your database state to the one your migrations suggest would be the case. You can then run rake db:schema:dump to update your schema.
I have two models connected with a has_and_belongs_to_many association: courses and semesters. rails_admin was only giving me the option to add semesters when creating a course, and not the other way around (and really, it's much more useful to add courses when creating a semester). I made some tweaks the migration:
def change
create_table "courses", force: :cascade do |t|
t.string "department"
t.integer "number"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "semesters", force: :cascade do |t|
t.integer "year"
t.string "season"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "semesters_courses", id: false, force: :cascade do |t|
t.integer "semester_id"
t.integer "course_id"
end
add_index "semesters_courses", ["course_id"], name: "index_semesters_courses_on_course_id"
add_index "semesters_courses", ["semester_id"], name: "index_semesters_courses_on_semester_id"
end
I renamed the intermediary table to semesters_courses from courses_semesters, just for clarity. Not only did this not solve the problem, but now when I try to add a new course, it 500s and tells me:
Could not find table 'courses_semesters'
I know I could make this go away by changing the name back, but I'm not sure where railsadmin is getting that name from (and suspect this to be the source of my problem). I've removed and reinstalled railsadmin, dropped and rewritten the tables, and cleared my browser's cache. When I search my entire project tree for "courses_semesters," I only get results in my error log.
New at Rails dev, so I assume I'm missing some config file somewhere that I need to update, but would love some help on where to find it.
You’re overwriting the join table name.
Option 1 you MUST specify the name of the join table in your models
app/models/course.rb
has_and_belongs_to_many :semesters, join_table: "semesters_courses"
app/models/semester.rb
has_and_belongs_to_many :courses, join_table: "semesters_courses"
Or Option 2 just rename your join table to "courses_semesters" by using migration.
rails g migration rename_courses_semesters
class RenameCoursesSemesters < ActiveRecord::Migration
def self.up
rename_table :semesters_courses, :courses_semesters
end
def self.down
rename_table :courses_semesters, :semesters_courses
end
end
Hope this answers your question.
I'm migrating a very old app from friendly_id 3.2 to 5.1.
I have a user model which currently has a cached_slug field. I created a new field called just slug. Initially, I thought I could just copy the data over from cached_slug to slug, but I noticed that there's also a whole other table called slugs which looks like this:
create_table "slugs", force: :cascade do |t|
t.string "name", limit: 255
t.integer "sluggable_id"
t.integer "sequence", default: 1, null: false
t.string "sluggable_type", limit: 40
t.string "scope", limit: 255
t.datetime "created_at"
end
Following the directions in the FriendlyID README for the Rails Quickstart, I ran rails generate friendly_id which created this table:
create_table "friendly_id_slugs", force: :cascade do |t|
t.string "slug", null: false
t.integer "sluggable_id", null: false
t.string "sluggable_type", limit: 50
t.string "scope"
t.datetime "created_at"
end
So now I'm all confused about what I need to do to complete migration. I tried creating a new user with the console and the friendly_id_slugs table is still empty, so I'm not sure when or what it's used for.
I have two questions:
1) What is this other table used for
2) What do I need to do to migrate my old slugs to the new table/field so it will continue to work moving forward?
Thanks!
If you don't mind losing the FriendlyId's History records (i.e: the old slugs),
drop the old slug table
in the rails console, run <ModelName>.find_each(&:save) for all friendly_id models.
Step 2 should regenerate new slugs.
Warning: Test before doing this on production servers!
Update: You can also perform step 2 in a migration file
class RegenerateSlugs < ActiveRecord::Migration
def change
# <ModelName>.find_each(&:save)
User.find_each(&:save)
Article.find_each(&:save)
end
end
My current schema looks like:
create_table "users", :force => true do |t|
t.string "username"
t.string "firstname"
t.string "lastname"
t.datetime "loggedin_at"
t.datetime "created_at"
t.datetime "updated_at"
t.integer `user_status`
end
I want to rename username to user_name, and make all the fields not null (they are currently nullable).
How would I do this? Do I create a migration file using rails generate, and then have to tweak it manually? How so?
It can help if you specify the Rails version number.
Before 3.0, it is:
Rails: How can I rename a database column in a Ruby on Rails migration?
If it is 3.0 or later, then you can look at the Migration documentation, such as rails generate instead of script/generate.