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How do I perform the SQL Join equivalent in MongoDB?
...rect. The new $lookup operator added to the aggregation pipeline is essentially identical to a left outer join:
https://docs.mongodb.org/master/reference/operator/aggregation/lookup/#pipe._S_lookup
From the docs:
{
$lookup:
{
from: <collection to join>,
localField: <...
What is the point of Lookup?
... via that key in an efficient manner (rather than just iterating over them all, which is what GroupBy lets you do).
For example, you could take a load of .NET types and build a lookup by namespace... then get to all the types in a particular namespace very easily:
using System;
using System.Collec...
What is a good Java library to zip/unzip files? [closed]
... zipFile.setPassword(password);
}
zipFile.extractAll(destination);
} catch (ZipException e) {
e.printStackTrace();
}
}
The Maven dependency is:
<dependency>
<groupId>net.lingala.zip4j</groupId>
<artifactId>zip4j</artifac...
Difference between Visibility.Collapsed and Visibility.Hidden
...have focus, you can't navigate to the control using the TAB key, etcetera, all of which still can if it would have a height and width of zero. But again, in terms of layout, you could say that.
– Razzie
May 20 '09 at 8:45
...
How to negate the whole regex?
...
How do I convert CamelCase into human-readable names in Java?
Regex for all strings not containing a string?
A regex to match a substring that isn’t followed by a certain other substring.
More examples
These are attempts to come up with regex solutions to toy problems as exercises; they shou...
How do I select the parent form based on which submit button is clicked?
...fferent). A user will only fill in one form, and I'd like to validate/etc all the forms with only one JS script.
5 Answers...
Can inner classes access private variables?
...ct of the parent class. You have to make the parent child relationship manually.
#include <string>
#include <iostream>
class Outer
{
class Inner
{
public:
Inner(Outer& x): parent(x) {}
void func()
{
std::string a =...
Entity Framework Join 3 Tables
.... I have the exact scenario but the query throws an exception [the_list_of_all_return_variables]' cannot be serialized . @marcinJuraszek - Could you have a look at stackoverflow.com/questions/42453123/…
– sandiejat
Feb 25 '17 at 7:15
...
CSS3 Rotate Animation
... Fiddle doesn't work o.O Chrome inspector does not like your CSS, specifically the "transform" and "transition-property". Oh dear.
– Just Plain High
Apr 5 '14 at 10:07
1
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Private virtual method in C++
...d, without further exposing the virtual functions directly by making them callable by derived classes (as would be possible if the functions were just protected). The point is that virtual functions exist to allow customization; unless they also need to be invoked directly from within derived classe...