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What's faster, SELECT DISTINCT or GROUP BY in MySQL?
...if you DON'T have an index (as it doesn't sort). When you do have an index and it's used, they're synonyms.
– Quassnoi
Feb 27 '09 at 15:11
10
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What is the difference between the add and offer methods in a Queue in Java?
... element can not be added to collection the add method throws an exception and offer doesn't.
From: http://java.sun.com/j2se/1.5.0/docs/api/java/util/Collection.html#add%28E%29
If a collection refuses to add a
particular element for any reason
other than that it already contains
the eleme...
How to use NSJSONSerialization
..."id": "2", "name":"Bbb"}]
This might give you a clear picture of how to handle it:
NSError *e = nil;
NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData: data options: NSJSONReadingMutableContainers error: &e];
if (!jsonArray) {
NSLog(@"Error parsing JSON: %@", e);
} else {
for...
What is an abstract class in PHP?
...act method, which is a method without any actual code in it, just the name and the parameters, and that has been marked as "abstract".
The purpose of this is to provide a kind of template to inherit from and to force the inheriting class to implement the abstract methods.
An abstract class thus is...
How do I find duplicates across multiple columns?
...
Duplicated id for pairs name and city:
select s.id, t.*
from [stuff] s
join (
select name, city, count(*) as qty
from [stuff]
group by name, city
having count(*) > 1
) t on s.name = t.name and s.city = t.city
...
Placement of the asterisk in pointer declarations
I've recently decided that I just have to finally learn C/C++, and there is one thing I do not really understand about pointers or more precisely, their definition.
...
How to override the copy/deepcopy operations for a Python object?
I understand the difference between copy vs. deepcopy in the copy module. I've used copy.copy and copy.deepcopy before successfully, but this is the first time I've actually gone about overloading the __copy__ and __deepcopy__ methods. I've already Googled around and looked through the ...
Have a div cling to top of screen if scrolled down past it [duplicate]
...has scrolled past it.
This is done with something like this, attaching a handler to the window.scroll event
// Cache selectors outside callback for performance.
var $window = $(window),
$stickyEl = $('#the-sticky-div'),
elTop = $stickyEl.offset().top;
$window.scroll(functi...
Do I encode ampersands in ?
I'm writing code that automatically generates HTML, and I want it to encode things properly.
4 Answers
...
Why do you need explicitly have the “self” argument in a Python method?
...quote Peters' Zen of Python. "Explicit is better than implicit."
In Java and C++, 'this.' can be deduced, except when you have variable names that make it impossible to deduce. So you sometimes need it and sometimes don't.
Python elects to make things like this explicit rather than based on a r...