大约有 23,000 项符合查询结果（耗时：0.0335秒） [XML]
Difference Between One-to-Many, Many-to-One and Many-to-Many?
...ps that you need to be concerned with when mapping. The first category is based on multiplicity and it includes three types:
*One-to-one relationships. This is a relationship where the maximums of each of its multiplicities is one, an example of which is holds relationship between Employee and P...
What are the differences between LinearLayout, RelativeLayout, and AbsoluteLayout?
...n align views one by one (vertically/ horizontally).
RelativeLayout means based on relation of views from its parents and other views.
ConstraintLayout is similar to a RelativeLayout in that it uses relations to position and size widgets, but has additional flexibility and is easier to use in the ...
Case in Select Statement
...earched CASE expression allows for values to be replaced in the result set based on comparison values. The following example displays the list price as a text comment based on the price range for a product.
USE AdventureWorks2012;
GO
SELECT ProductNumber, Name, "Price Range" =
CASE
...
Paperclip::Errors::MissingRequiredValidatorError with Rails 4
...s_attachment_content_type in Model
Rails 3
class User < ActiveRecord::Base
attr_accessible :avatar
has_attached_file :avatar, :styles => { :medium => "300x300>", :thumb => "100x100>" }, :default_url => "/images/:style/missing.png"
validates_attachment_content_type :avatar, :co...
`static` keyword inside function?
... static $cache = null;
if ($cache === null) {
$cache = '%heavy database stuff or something%';
}
// code using $cache
}
In this example, the if would only be executed once. Even if multiple calls to doStuff would occur.
...
belongs_to through associations
...
You can also delegate:
class Company < ActiveRecord::Base
has_many :employees
has_many :dogs, :through => :employees
end
class Employee < ActiveRescord::Base
belongs_to :company
has_many :dogs
end
class Dog < ActiveRecord::Base
belongs_to :employee
deleg...
How to create SBT project with IntelliJ Idea?
...g. Afterwards one can just do File -> New Project -> Scala -> SBT based. IntelliJ will generate basic build.sbt, download necessary dependencies and open project.
SBT Plugin
Sbt plugin that generate an idea project based on the sbt files can be found here: https://github.com/mpeltonen/sb...
SQLAlchemy: cascade delete
...ld object from parent.children, should that object be deleted from the database, or should only it's reference to the parent be removed (ie. set parentid column to null, instead of deleting the row)
– Steven
Feb 8 '16 at 13:04
...
Update multiple rows in same query using PostgreSQL
...
Based on the solution of @Roman, you can set multiple values:
update users as u set -- postgres FTW
email = u2.email,
first_name = u2.first_name,
last_name = u2.last_name
from (values
(1, 'hollis@weimann.biz', 'Holli...
Load dimension value from res/values/dimension.xml from source code
...etrieve a dimensional for a particular resource ID. Unit conversions
are based on the current DisplayMetrics associated with the resources.
so if you want exact dp value just as in xml just divide it with DisplayMetrics density
int dp = (int) (getResources().getDimension(R.dimen.test) / getReso...