目的

テーブル作成を行なった際にmigrateでエラーが出た話をまとめる

エラー内容

下記コマンドでモデルファイルを作成した。
```
$ rails g model user name:string
```
その後、下記コマンドでmigreteを実行した。
```
$ rails db:migrate
```

下記のエラーが発生した

[14:50:10]MacBook-miriwo~/workspace/study/rails/tropical_fish_sns_of_rails$ rails db:migrate
== 20200206055010 CreateUsers: migrating ======================================
-- create_table(:users)
rails aborted!
StandardError: An error has occurred, all later migrations canceled:

Mysql2::Error: Table 'users' already exists
/Users/admin/workspace/study/rails/tropical_fish_sns_of_rails/db/migrate/20200206055010_create_users.rb:3:in `change'
/Users/admin/workspace/study/rails/tropical_fish_sns_of_rails/bin/rails:9:in `<top (required)>'
/Users/admin/workspace/study/rails/tropical_fish_sns_of_rails/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'

Caused by:
ActiveRecord::StatementInvalid: Mysql2::Error: Table 'users' already exists
/Users/admin/workspace/study/rails/tropical_fish_sns_of_rails/db/migrate/20200206055010_create_users.rb:3:in `change'
/Users/admin/workspace/study/rails/tropical_fish_sns_of_rails/bin/rails:9:in `<top (required)>'
/Users/admin/workspace/study/rails/tropical_fish_sns_of_rails/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'

Caused by:
Mysql2::Error: Table 'users' already exists
/Users/admin/workspace/study/rails/tropical_fish_sns_of_rails/db/migrate/20200206055010_create_users.rb:3:in `change'
/Users/admin/workspace/study/rails/tropical_fish_sns_of_rails/bin/rails:9:in `<top (required)>'
/Users/admin/workspace/study/rails/tropical_fish_sns_of_rails/bin/spring:15:in `<top (required)>'
bin/rails:3:in `load'
bin/rails:3:in `<main>'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

原因調査

下記コマンドを実行して現在のmigrateのステータスを確認した。
```
$ rails db:migrate:status
```

以前にmigrateを実施した際のmigrationファイルのが無いことが判明した。

[14:52:57]MacBook- 
miriwo~/workspace/study/rails/tropical_fish_sns_of_rails/db/migrate$ rails db:migrate:status

database: tropical_fish_sns_development

 Status   Migration ID    Migration Name
--------------------------------------------------
   up     20200206025324  ********** NO FILE **********
   up     20200206025916  ********** NO FILE **********
  down    20200206055010  Create users

解決法

下記コマンドを実行してDBのリセットを行なった。
```
$ rails db:migrate:reset
```

DBの状態を確認した。

[14:54:33]MacBook-miriwo~/workspace/study/rails/tropical_fish_sns_of_rails/db/migrate$ rake 
db:migrate:status
(in /Users/admin/workspace/study/rails/tropical_fish_sns_of_rails)

database: tropical_fish_sns_development

 Status   Migration ID    Migration Name
--------------------------------------------------
   up     20200206055010  Create users

正常に反映されていることをがわかった。