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data.frame rows to a list
I have a data.frame which I would like to convert to a list by rows, meaning each row would correspond to its own list elements. In other words, I would like a list that is as long as the data.frame has rows.
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Rails migration for has_and_belongs_to_many join table
...here:
class Teacher < ActiveRecord::Base
has_and_belongs_to_many :students
end
and
class Student < ActiveRecord::Base
has_and_belongs_to_many :teachers
end
for rails 4:
rails generate migration CreateJoinTableStudentTeacher student teacher
for rails 3:
rails generate migrati...
How to set a default value for a datetime column to record creation time in a migration?
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This is supported now in Rails 5.
Here is a sample migration:
class CreatePosts < ActiveRecord::Migration[5.0]
def change
create_table :posts do |t|
t.datetime :modified_at, default: -> { 'CURRENT_TIMESTAMP' }
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What's the foolproof way to tell which version(s) of .NET are installed on a production Windows Serv
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Uses for the Java Void Reference Type?
There is a Java Void -- uppercase V-- reference type . The only situation I have ever seen it used is to parameterize Callable s
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MySQL “incorrect string value” error when save unicode string in Django
...trange error message when tried to save first_name, last_name to Django's auth_user model.
9 Answers
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The new keyword “auto”; When should it be used to declare a variable type? [duplicate]
Have we (as a community) had enough experience to determine when and/or whether auto is being abused?
6 Answers
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How to keep environment variables when using sudo
When I use any command with sudo the environment variables are not there. For example after setting HTTP_PROXY the command wget works fine without sudo . However if I type sudo wget it says it can't bypass the proxy setting.
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Use tab to indent in textarea
I have a simple html textarea on my side. Right now if you click tab in it, it goes to the next field. I would like to make the tab button indent a few spaces instead. How can I do this? Thanks.
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MySQL DROP all tables, ignoring foreign keys
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I found the generated set of drop statements useful, and recommend these tweaks:
Limit the generated drops to your database like this:
SELECT concat('DROP TABLE IF EXISTS `', table_name, '`;')
FROM information_schema.tables...