问题描述
我想在 Ruby on Rails 迁移脚本中创建一列 unique.最好的方法是什么?还有一种方法可以索引表中的列吗?
I would like to make a column unique in Ruby on Rails migration script. What is the best way to do it? Also is there a way to index a column in a table?
我想在数据库中强制使用 unique 列，而不是仅使用 :validate_uniqueness_of.
I would like to enforce unique columns in a database as opposed to just using :validate_uniqueness_of.
推荐答案
旧版本 Rails 的简短答案(请参阅 Rails 4+ 的其他答案):
The short answer for old versions of Rails (see other answers for Rails 4+):
add_index :table_name, :column_name, unique: true
要同时索引多个列，您需要传递一个列名数组而不是单个列名，
To index multiple columns together, you pass an array of column names instead of a single column name,
add_index :table_name, [:column_name_a, :column_name_b], unique: true
如果您得到索引名称...太长"，您可以在 add_index 方法中添加 name: "whatever" 以缩短名称.
If you get "index name... is too long", you can add name: "whatever" to the add_index method to make the name shorter.
对于细粒度控制，有一个execute"方法可以直接执行 SQL.
For fine-grained control, there's a "execute" method that executes straight SQL.
就是这样！
如果您要这样做来代替常规的旧模型验证，请检查它是如何工作的.如果没有模型级别的验证，向用户报告的错误可能不会那么好.你总是可以同时做到这两点.
If you are doing this as a replacement for regular old model validations, check to see how it works. The error reporting to the user will likely not be as nice without model-level validations. You can always do both.
这篇关于如何在 Ruby on Rails 迁移中使列唯一并为其编制索引?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！