Ruby on Rails 的 varchar 迁移问题
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varchar Migration question for Ruby on Rails
提问by bgadoci
I have created a new table including a column "note". The default is varchar(255) I believe but I wish to have this column be a text area vs. a field and to allow more data. I imagine that I would make this change in ActiveRecord::Migration file but I am curious as to the format. Do I simply change the varchar(255) to varchar(1000) for example? (if so what is the format?
我创建了一个包含“注释”列的新表。我相信默认值是 varchar(255) 但我希望此列是文本区域而不是字段并允许更多数据。我想我会在 ActiveRecord::Migration 文件中进行此更改，但我对格式很好奇。例如，我是否只需将 varchar(255) 更改为 varchar(1000) ？（如果是，格式是什么？
def self.up
create_table :notes do |t|
t.string :note :varchar(1000)
end
Is that the right format? Furthermore, how do I get the entry field to be multiple rows. Sorry if this is easy stuff but I am new to programming and RoR. Thanks.
这是正确的格式吗？此外，如何让输入字段成为多行。对不起，如果这是简单的东西，但我是编程和 RoR 的新手。谢谢。
采纳答案by Siddhartha Reddy
You can simply use the 'text' type instead of 'string'.
您可以简单地使用“文本”类型而不是“字符串”。
def self.up
create_table :notes do |t|
t.text :note
end
end
Using the 'text' type will result in database column of type TEXT. Varchar is usually limited to a maximum length of 255 (in MySQL, other RDBMSs have similar limits).
使用 'text' 类型将导致 TEXT 类型的数据库列。Varchar 通常限制为最大长度 255（在 MySQL 中，其他 RDBMS 也有类似的限制）。
If you use Rails' form helpers, a textareawill be output for this field (because it is of type 'text'). textareais the form element that accepts multi-line input.
如果您使用 Rails 的表单助手，则会为该字段输出一个文本区域（因为它是“文本”类型）。textarea是接受多行输入的表单元素。
Edit: If you've already migrated the create_table, you can create a new migration to change the column type:
编辑：如果您已经迁移了 create_table，您可以创建一个新的迁移来更改列类型：
def self.up
change_column :notes, :note, :text
end
回答by The Who
The correct format would be
正确的格式是
t.string :note, :limit => 1000make sure you are using a version of MySQL(or whichever database) which supports varchars longer than 256 characters.
确保您使用的是支持长度超过 256 个字符的 varchars 的 MySQL（或任何数据库）版本。
if you want to use a large text block it would be
如果你想使用大文本块，那就是
t.text :noteSee http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/TableDefinition.htmlfor more information
有关更多信息，请参阅http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html
回答by Ben Crouse
You can change the length with the limit option as so...
您可以使用限制选项更改长度，因此...
def self.up
change_column :notes, :note, :string, :limit => 1000
end
回答by roberocity
Since I had a lot of data already stored I used
由于我已经存储了很多数据，因此我使用了
self.up
change_column :notes, :note, :text, :limit => nil
end
If I left off the :limit => nil option then the column type would change from varchar to text, but it still had a max length of 255 characters.
如果我不使用 :limit => nil 选项，那么列类型将从 varchar 更改为 text，但它的最大长度仍为 255 个字符。
