mysql - Rails 控制台不同的 MySQL 结果

Question

我在 Rails 中使用 LEFT OUTER JOIN 时遇到问题。我想我已经有了 Ruby 代码，但是当我将其输入到 Rails 控制台时，我得到一个结果，而当我复制生成的 MySQL 时，我得到另一个结果。 rails 控制台 中缺少整个列(值)。为什么 SQL 完全相同但结果不同？理想情况下，我希望结果包含值列。一如既往，任何帮助将不胜感激。

Rails 控制台响应

2.0.0-p353 :023 > SecurityItem.joins("LEFT OUTER JOIN  security_role_permissions ON security_role_permissions.security_item_id = security_items.id  AND security_role_permissions.role_id ='1'").select("security_items.name, security_role_permissions.value")

 SecurityItem Load (0.7ms)  SELECT security_items.name, security_role_permissions.value FROM `security_items` LEFT OUTER JOIN security_role_permissions ON security_role_permissions.security_item_id = security_items.id AND security_role_permissions.role_id ='1

=> #<ActiveRecord::Relation 
[#<SecurityItem id: nil, key: "ChangePassword", name: "Change Password">, 
 #<SecurityItem id: nil, key: "AddUsers", name: "Add Users">, 
 #<SecurityItem id: nil, key: "UpdateUsers", name: "Update Users">, 
 #<SecurityItem id: nil, key: "DeleteUsers", name: "Delete Users">]> 

MySQL 响应

mysql>  SELECT security_items.name, security_role_permissions.value FROM `security_items` LEFT OUTER JOIN security_role_permissions ON security_role_permissions.security_item_id = security_items.id AND security_role_permissions.role_id ='1';

+-----------------+-------+
| name            | value |
+-----------------+-------+ 
| Change Password |     1 |
| Add Users       |  NULL |
| Update Users    |  NULL |
| Delete Users    |  NULL |
+-----------------+-------+

Answer 1

只有来自 SecurityItem 类的属性才会出现在返回结果中。但是，您可以通过“attributes”方法访问连接表中的属性。

security_items = SecurityItem.joins("LEFT OUTER JOIN  security_role_permissions 
ON security_role_permissions.key = security_items.key  AND
security_role_permissions.role_id ='1'").select("security_items.name, 
security_items.key, security_role_permissions.permission")

security_items.each { |security_item| puts security_item.attributes['permission'] }