my rails db:migrate isnt working - ruby-on-rails

Question

i tried running rake bd:migrate but it gave me an error and told me to run rails db:migrate RAILS_ENV=development instead but it gave me bunch of errors
C:\Sites\seekhostel.com>rails db:migrate RAILS_ENV=development
== 20180311182801 AddDeviseToUsers: migrating =================================
-- change_table(:users)
rails aborted!
StandardError: An error has occurred, this and all later migrations canceled:
SQLite3::SQLException: duplicate column name: email: ALTER TABLE "users" ADD "email" varchar DEFAULT '' NOT NULL
C:/Sites/seekhostel.com/db/migrate/20180311182801_add_devise_to_users.rb:7:in `block in up'
C:/Sites/seekhostel.com/db/migrate/20180311182801_add_devise_to_users.rb:5:in `up'
bin/rails:4:in `require'
bin/rails:4:in `<main>'
Caused by:
ActiveRecord::StatementInvalid: SQLite3::SQLException: duplicate column name: email: ALTER TABLE "users" ADD "email" varchar DEFAULT '' NOT NULL
C:/Sites/seekhostel.com/db/migrate/20180311182801_add_devise_to_users.rb:7:in `block in up'
C:/Sites/seekhostel.com/db/migrate/20180311182801_add_devise_to_users.rb:5:in `up'
bin/rails:4:in `require'
bin/rails:4:in `<main>'
Caused by:
SQLite3::SQLException: duplicate column name: email
C:/Sites/seekhostel.com/db/migrate/20180311182801_add_devise_to_users.rb:7:in `block in up'
C:/Sites/seekhostel.com/db/migrate/20180311182801_add_devise_to_users.rb:5:in `up'
bin/rails:4:in `require'
bin/rails:4:in `<main>'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)
i would love to know why it did so and how to fix it

Answer 1

By looking at error message I suspect two things happened here:
You already had users table (because new migration has change_table(:users), not create_table(:users) - devise generator recognize that)
You ran $ rails generate devise command and you didn't inspect autogenerated migration file.
You were supposed to remove line
t.string :email, null: false, default: ""
from 20180311182801_add_devise_to_users.rb file