Ruby-on-rails Rails 4：向现有表添加多列
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Rails 4: Add Multiple Columns to Existing Table
提问by Sylar
I know how to add one column to an existing table. Now I have to add many columns to an existing table. Is there a shorter way for:
我知道如何向现有表中添加一列。现在我必须向现有表中添加许多列。是否有更短的方法：
add_col1_col2_col3_col4_.._coln_to_tables col1:integer col2:integer etc...
Do I have to do the above for ALL the additional columns I have to add?
我是否必须为我必须添加的所有附加列执行上述操作？
回答by Shweta
No not necessary. You can do
没有没有必要。你可以做
Assuming TableName is user
假设表名是用户
rails g migration AddColumnsToUser col1:integer col2:integer .. etc.
回答by Proto
Here's a good resource on ActiveRecord:Migrationswhich lists all the commands you can use to manipulate your databases. You can also do the task this way:
这是ActiveRecord:Migrations上的一个很好的资源，其中列出了可用于操作数据库的所有命令。您也可以通过以下方式完成任务：
rails g migration AddMoreColumnsToModel
rails g migration AddMoreColumnsToModel
Then open the migration file and put:
然后打开迁移文件并输入：
def change
add_column :table, :new_column, :type
# add as many columns as you need
end
If you wanted to do what Maxd suggests, having literally 100 columns of the same type auto-create, his code is a good idea.
如果您想按照 Maxd 的建议进行操作，即自动创建 100 列相同类型的列，那么他的代码是一个好主意。
回答by Maxim
Just create migration and generate these columns i.e.:
只需创建迁移并生成这些列，即：
class ChangeTables < ActiveRecord::Migration
def change
change_table :tables do |t|
100.times do |i|
t.integer :"column_#{i}"
end
end
end
end
回答by Dinesh Pallapa
Similar to above answers but for understanding purpose hope below naming convention is good.
类似于上面的答案，但为了理解目的，希望下面的命名约定是好的。
rails g migration add_first_column_and_second_column_to_model first_column:string second_column:string
回答by IcyBright
This migration file can be done in a loop. But do you really want to do this? It does not look correct to create such a heavy model to hold everything.
这个迁移文件可以循环完成。但你真的想这样做吗？创建如此沉重的模型来容纳所有东西看起来并不正确。
回答by puneet18
command to create new modeland tablewith columns:
创建new model和table使用命令columns：
rails g model ModelName col_name1:string col_name2:integer col_name3:text ...
command to add more columnsunder existing table:
命令columns在现有表下添加更多：
rails g migration AddColumnToModelName col_name4:string col_name5:integer ...
At last, run migrationby command:
最后，migration通过命令运行：
rake db:migrate
