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How do I find duplicates across multiple columns?
...simple and efficient means to locate unwanted repetition, whilst also list all affected rows and all wanted columns:
SELECT
t.*
FROM (
SELECT
s.*
, COUNT(*) OVER (PARTITION BY s.name, s.city) AS qty
FROM stuff s
) t
WHERE t.qty > 1
ORDER BY t.name, t.city
While most...
How to “EXPIRE” the “HSET” child key in redis?
I need to expire all keys in redis hash, which are older than 1 month.
11 Answers
11
...
Adding a Method to an Existing Object Instance
...that instance will be passed as the first argument whenever the method is called.
Callables that are attributes of a class (as opposed to an instance) are still unbound, though, so you can modify the class definition whenever you want:
>>> def fooFighters( self ):
... print "fooFighters...
C++0x has no semaphores? How to synchronize threads?
...ck Overflow regarding the use of semaphores. I use them (posix semaphores) all the time to let a thread wait for some event in another thread:
...
How to get a pixel's x,y coordinate color from an image?
...http://jsfiddle.net/thirtydot/9SEMf/869/ I used jQuery for convenience in all of this, but it is by no means required.
Note: getImageData falls under the browser's same-origin policy to prevent data leaks, meaning this technique will fail if you dirty the canvas with an image from another domain o...
How to initialize a private static const map in C++?
... int>’ as ‘this’ argument of ‘std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const key_type&) [with _Key = int; _Tp = int; _Compare = std::less<int>; _Alloc = std::allocator<std::pair<const int, int>...
visual c++: #include files from other projects in the same solution
...ive I've come across. Well done and thanks!
– David Hall
Apr 13 '11 at 11:50
9
There was a sugges...
What's the difference between utf8_general_ci and utf8_unicode_ci?
...languages or characters.
On modern servers, this performance boost will be all but negligible. It was devised in a time when servers had a tiny fraction of the CPU performance of today's computers.
Benefits of utf8mb4_unicode_ci over utf8mb4_general_ci
utf8mb4_unicode_ci, which uses the Unicode r...
“Diff” an image using ImageMagick
... as a PNG file, the second one as a PDF.
The resulting diff file displays all pixels which are different in red color. The ones which are unchanged appear white.
Short and sweet.
Note, your images need not be the same type. You can even mix JPEG, TIFF, PNG -- under one condition: the images sho...
Why escape_javascript before rendering a partial?
I'm looking at this Railscast episode and wondering why the call to escape_javascript is needed here:
4 Answers
...