This is a workaround that was taken when a new table was created and rails db: migrate was executed during Rails learning, but it was not reflected in the DB (DB Browser for SQlite).
ActiveRecord::Base.connection.execute("BEGIN TRANSACTION; END;")
I entered this command with rails consoloe and it was fixed.
https://qiita.com/shun_study_p/items/fbb4cb2d4c392063c9a9
I referred to the article at the above URL.