Ruby-on-rails 查找存在属性的记录
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Find records where an attribute is present
提问by Fellow Stranger
I have a Usermodel with the attributes username, emailand name.
我有一个User具有属性的模型username,email和name.
usernameand emailare required upon signup, but not name.
username并且email在注册时是必需的，但不是name。
What would be the query to find all users that have filled out name(i.e. it is no nil)?
查找所有已填写的用户name（即不为零）的查询是什么？
The query should be at least Rails 3.2 and 4.0 compatible.
查询至少应与 Rails 3.2 和 4.0 兼容。
I'm thinking something in the lines of:
我在想以下几点：
User.where(name: present?)
采纳答案by fiedl
present?
展示？
present?is essentially not nil and not empty?:
present?本质上是not nil and not empty?：
class Object
def present?
!blank?
end
def blank?
respond_to?(:empty?) ? !!empty? : !self
end
end
ActiveRecord condition
活动记录条件
In Rails 4, not conditionscan be done without raw sql code.
在 Rails 4 中，没有原始 sql 代码就无法完成条件。
# Both lines lead to the same result:
User.where.not(name: [nil, ""])
User.where.not(name: nil).where.not(name: "")
Since there is no raw sql code, you don't have to worry about if they work with every database adapter. In fact, this works fine for both, mysql and postgres.
由于没有原始 sql 代码，您不必担心它们是否适用于每个数据库适配器。事实上，这对 mysql 和 postgres 都适用。
to_sql
to_sql
You can see how they translate to sql queries if you append .to_sql, for example in the rails console.
如果您 append .to_sql，您可以看到它们如何转换为 sql 查询，例如在 rails 控制台中。
# rails console
User.where.not(name: [nil, ""]).to_sql
# => "SELECT \"users\".* FROM \"users\" WHERE (NOT ((\"users\".\"name\" = '' OR \"users\".\"name\" IS NULL)))"
User.where.not(name: nil).where.not(name: "").to_sql
# => "SELECT \"users\".* FROM \"users\" WHERE (\"users\".\"name\" IS NOT NULL) AND (\"users\".\"name\" != '')"
Further Reading
进一步阅读
回答by nathanvda
An empty value in a database gets a special value NULL. Testing whether is set uses the special comparator IS NULLor IS NOT NULL.
数据库中的空值获得一个特殊值NULL。测试是否设置使用特殊比较器IS NULL或IS NOT NULL。
Then there still remains the possibility that an empty string was filled in, so a complete test would be
然后仍然存在填充空字符串的可能性，因此完整的测试将是
@users = User.where("name is NOT NULL and name != ''")
[UPDATED for rails 4+]
[已更新 Rails 4+]
Since rails 4 we can write:
从 rails 4 开始，我们可以这样写：
User.where.not(name: [nil, ""])
which will generate the same query. Awesome :)
这将生成相同的查询。惊人的 ：）
回答by gstraehle
NOT SQL queries can be built by where.not
可以通过 where.not 构建 NOT SQL 查询
@users = User.where.not(name: nil)
回答by Nobita
Try this:
尝试这个：
User.where("name IS NOT NULL AND name != ?", "")
I edited my answer as per @nathavanda comments, which his answer in my opinion should be the accepted one.
我根据@nathavanda 的评论编辑了我的答案，在我看来，他的答案应该是公认的答案。
回答by yoones
Rails 3 sort after .where condition using NOT NULL
Rails 3 在 .where 条件之后使用 NOT NULL 排序
@users = User.where('name IS NOT NULL')
