When I created a migration file as usual and tried rails db: migrate, I got the following error.
Column user_id on table entries does not match column id on users, which has type bigint(20). To resolve this issue, change the type of the user_id column on entries to be :bigint. (For example t.bigint :user_id).
As instructed, the migration was performed again by specifying bigint as shown below.
class CreateEntries < ActiveRecord::Migration[5.1]
  def change
    create_table :entries do |t|
      t.references :user, foreign_key: true, type: :bigint //Change from integer to bigint
      t.references :room, foreign_key: true
      t.timestamps
    end
  end
end```
 However, a similar error appeared.
 Actually, at this time, three migration files were created at the same time, and an error occurred because the creation date and time of the migration file (room) required to register the above migration file was the last.
 I changed the file name to the creation date and time of the room file, and when I ran rails db: migrate again, it passed without problems.