migrate error

i have problem with 'rake db:migrate'

i use this tutorial =>

form first step to this step.

when i type 'rake db:migrate' in my terminal.

i get this error =>

== 20160127215334 Books: migrating

The error indicates that the migration calls for the creation of the
books table, but that table already exists.


Colin Law wrote in post #1180957:

Examine the database using whatever utility you use for doing that ( I
think it is psql for postgres, I guess there are also graphical
utilities) and I suspect you will find you have. Perhaps you have
accidentally added two migrations for adding the table, or perhaps you
have managed to run the migration twice. If you have nothing of
interest in the db than you can throw it away and start again using

rake db:drop # delete the db
rake db:create # create an empty one
rake db:migrate # run the migrations