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How do I perform the SQL Join equivalent in MongoDB?
...ttps://docs.mongodb.org/master/reference/operator/aggregation/lookup/#pipe._S_lookup
From the docs:
{
$lookup:
{
from: <collection to join>,
localField: <field from the input documents>,
foreignField: <field from the documents of the "from" collection>...
Can I create links with 'target=“_blank”' in Markdown?
...d, you'll just have to use HTML.
<a href="http://example.com/" target="_blank">Hello, world!</a>
Most Markdown engines I've seen allow plain old HTML, just for situations like this where a generic text markup system just won't cut it. (The StackOverflow engine, for example.) They then...
How to convert a scala.List to a java.util.List?
...1,2,3))
From Scala 2.8 onwards:
import scala.collection.JavaConversions._
import scala.collection.mutable.ListBuffer
asList(ListBuffer(List(1,2,3): _*))
val x: java.util.List[Int] = ListBuffer(List(1,2,3): _*)
However, asList in that example is not necessary if the type expected is a Java List,...
What is the difference between a field and a property?
...It is private to your class and stores the actual data.
private string _myField;
// this is a property. When accessed it uses the underlying field,
// but only exposes the contract, which will not be affected by the underlying field
public string MyProperty
{
get
...
Syntax Error: Not a Chance
...indentation will never be implemented.
Normally, imports from the special __future__ module enable features that are backwards-incompatible, such as the print() function, or true division.
So the line from __future__ import braces is taken to mean you want to enable the 'create blocks with braces'...
Select count(*) from multiple tables
...
Just because it's slightly different:
SELECT 'table_1' AS table_name, COUNT(*) FROM table_1
UNION
SELECT 'table_2' AS table_name, COUNT(*) FROM table_2
UNION
SELECT 'table_3' AS table_name, COUNT(*) FROM table_3
It gives the answers transposed (one row per table instead of ...
Python JSON serialize a Decimal object
...
The problem was that DecimalEncoder()._iterencode(decimal.Decimal('3.9')).next() returned the correct '3.9', but DecimalEncoder()._iterencode(3.9).next() returned a generator object which would only return '3.899...' when you piled on another .next(). Generator f...
Nested classes' scope?
...
class Outer(object):
outer_var = 1
class Inner(object):
@property
def inner_var(self):
return Outer.outer_var
This isn't quite the same as similar things work in other languages, and uses global lookup instead of sco...
Calling constructors in c++ without new
...d the most common way of creating new dynamic objects instead of using auto_ptr, unique_ptr, or related.
– Fred Nurk
Jan 18 '11 at 13:18
3
...
Best practice for Django project working directory structure
...cts, but doesn't have to be. It usually looks like this:
~/projects/project_name/
docs/ # documentation
scripts/
manage.py # installed to PATH via setup.py
project_name/ # project dir (the one which django-admin.py creates)
apps/ # project-specific applic...