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How to include “zero” / “0” results in COUNT aggregate?
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LEFT JOIN appointment ON person.person_id = appointment.person_id
GROUP BY person.person_id;
The reason why this is working, is that the outer (left) join will return NULL for those persons that do not have an appointment. The aggregate function count() will not count NULL values and thus you'l...
When should we use mutex and when should we use semaphore
...a mutex when you (thread) want to execute code that should not be executed by any other thread at the same time. Mutex 'down' happens in one thread and mutex 'up' must happen in the same thread later on.
e.g.: If you are deleting a node from a global linked list, you do not want another thread to mu...
How to show disable HTML select option in by default?
... You don't need to put the true or disabled values. you can get by doing <option selected disabled>Choose Tagging</option>
– Sam Eaton
Feb 17 '16 at 3:37
19
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Turning off “created by” stamp when generating files in IntelliJ
... Code Templates area of the settings dialog. In Idea 15+ you can get there by typing ctrl+shift+A on windows or cmd+shift+A on osx and then typing Include Templates in the popup action search dialog. There should be a tab called Includes on which you will find the Java and ActionScript file types, a...
Difference between thread's context class loader and normal classloader
... be created from a class in ClassLoaderC and then passed to a thread owned by ClassLoaderD. In this case the object needs to use Thread.currentThread().getContextClassLoader() directly if it wants to load resources that are not available on its own classloader.
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What's the best way to get the last element of an array without deleting it?
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option .1. $x = array_values(array_slice($array, -1))[0]; (as suggested by rolacja)
option .2. $x = array_slice($array, -1)[0]; (as suggested by Stoutie)
option .3. $x = array_pop((array_slice($array, -1))); (as suggested by rolacja)
option .4. $x = array_pop((array_slice($array, -1, 1))); (as su...
Why does ++[[]][+[]]+[+[]] return the string “10”?
...y A to avoid the wrong notation.
++ before its operand means “increment by one and return the incremented result”. So ++[[]][0] is equivalent to Number(A) + 1 (or +A + 1).
Again, we can simplify the mess into something more legible. Let's substitute [] back for A:
(+[] + 1)
+
[0]
Before +[]...
Is nested function a good approach when required by only one function? [closed]
Let's say that a function A is required only by function B , should A be defined inside B?
12 Answers
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Using arrays or std::vectors in C++, what's the performance gap?
...operations on vectors and arrays/pointers.
// Assembly code was generated by gcc 4.1.0 invoked with g++ -O3 -S on a
// x86_64-suse-linux machine.
#include <vector>
struct S
{
int padding;
std::vector<int> v;
int * p;
std::vector<int>::iterator i;
};
int pointer_inde...
Combined area of overlapping circles
...circles is the area of the polygon + the area of the circle slices defined by consecutive intersection points and the circle center in between them. You'll need to also account for any holes.
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