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author | Vijay Dev <vijaydev.cse@gmail.com> | 2015-08-24 06:05:07 +0000 |
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committer | Vijay Dev <vijaydev.cse@gmail.com> | 2015-08-24 06:05:07 +0000 |
commit | 4f252cddc1ee4e28c633a2250335b2fac4d31108 (patch) | |
tree | 776177555c7039204e23c9c1b7d33b700d366ca3 /guides/source/active_record_migrations.md | |
parent | bc36ffeec05692777f4ece09978a321feed2d818 (diff) | |
parent | 06818cb9a8cee8c95eaebdd1418e6fcb0da9382e (diff) | |
download | rails-4f252cddc1ee4e28c633a2250335b2fac4d31108.tar.gz rails-4f252cddc1ee4e28c633a2250335b2fac4d31108.tar.bz2 rails-4f252cddc1ee4e28c633a2250335b2fac4d31108.zip |
Merge branch 'master' of github.com:rails/rails
Conflicts:
guides/source/security.md
Diffstat (limited to 'guides/source/active_record_migrations.md')
-rw-r--r-- | guides/source/active_record_migrations.md | 31 |
1 files changed, 17 insertions, 14 deletions
diff --git a/guides/source/active_record_migrations.md b/guides/source/active_record_migrations.md index ce605c912e..4e5902fb3d 100644 --- a/guides/source/active_record_migrations.md +++ b/guides/source/active_record_migrations.md @@ -357,8 +357,8 @@ will append `ENGINE=BLACKHOLE` to the SQL statement used to create the table ### Creating a Join Table -Migration method `create_join_table` creates an HABTM join table. A typical use -would be: +The migration method `create_join_table` creates an HABTM (has and belongs to +many) join table. A typical use would be: ```ruby create_join_table :products, :categories @@ -367,23 +367,21 @@ create_join_table :products, :categories which creates a `categories_products` table with two columns called `category_id` and `product_id`. These columns have the option `:null` set to `false` by default. This can be overridden by specifying the `:column_options` -option. +option: ```ruby -create_join_table :products, :categories, column_options: {null: true} +create_join_table :products, :categories, column_options: { null: true } ``` -will create the `product_id` and `category_id` with the `:null` option as -`true`. - -You can pass the option `:table_name` when you want to customize the table -name. For example: +By default, the name of the join table comes from the union of the first two +arguments provided to create_join_table, in alphabetical order. +To customize the name of the table, provide a `:table_name` option: ```ruby create_join_table :products, :categories, table_name: :categorization ``` -will create a `categorization` table. +creates a `categorization` table. `create_join_table` also accepts a block, which you can use to add indices (which are not created by default) or additional columns: @@ -1006,7 +1004,10 @@ such features, the `execute` method can be used to execute arbitrary SQL. Migrations and Seed Data ------------------------ -Some people use migrations to add data to the database: +The main purpose of Rails' migration feature is to issue commands that modify the +schema using a consistent process. Migrations can also be used +to add or modify data. This is useful in an existing database that can't be destroyed +and recreated, such as a production database. ```ruby class AddInitialProducts < ActiveRecord::Migration @@ -1022,9 +1023,11 @@ class AddInitialProducts < ActiveRecord::Migration end ``` -However, Rails has a 'seeds' feature that should be used for seeding a database -with initial data. It's a really simple feature: just fill up `db/seeds.rb` -with some Ruby code, and run `rake db:seed`: +To add initial data after a database is created, Rails has a built-in +'seeds' feature that makes the process quick and easy. This is especially +useful when reloading the database frequently in development and test environments. +It's easy to get started with this feature: just fill up `db/seeds.rb` with some +Ruby code, and run `rake db:seed`: ```ruby 5.times do |i| |