> For the complete documentation index, see [llms.txt](https://kelby.gitbook.io/rails-beginner-s-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kelby.gitbook.io/rails-beginner-s-guide/activerecord_migration/activerecord_migrator_schema_relates.md).

# Schema

继承于 Migration

常用的如：

```
define
```

对应的是 db/schema.rb 里的方法，举例：

```ruby
ActiveRecord::Schema.define(version: 20380119000001) do
  # ...
end
```

再举例：

```ruby
require 'active_record'
ActiveRecord::Base.establish_connection( adapter: 'sqlite3', database: ":memory:" )
ActiveRecord::Schema.define(version: 1) { create_table(:articles) { |t| t.string :title } }

class Article < ActiveRecord::Base; end

Article.create title: 'Quick brown fox'
```

其它方法：

```
migrations_paths
```

> Note: 它里面不支持非 migration 语句，也就是说直接让它执行 SQL 语句是不行的。