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Retrieving the last record in each group - MySQL
...dowing functions, like almost all popular SQL implementations. With this standard syntax, we can write greatest-n-per-group queries:
WITH ranked_messages AS (
SELECT m.*, ROW_NUMBER() OVER (PARTITION BY name ORDER BY id DESC) AS rn
FROM messages AS m
)
SELECT * FROM ranked_messages WHERE rn = 1...
How can I get a JavaScript stack trace when I throw an exception?
...n simply call: console.trace(); (MDN Reference)
Edit 1 (2013):
A better (and simpler) solution as pointed out in the comments on the original question is to use the stack property of an Error object like so:
function stackTrace() {
var err = new Error();
return err.stack;
}
This will ge...
Where does System.Diagnostics.Debug.Write output appear?
...built with csc hello.cs ) prints just Hello via Console! on the console and Hello via OutputDebugString in the DebugView window. However, I cannot see either of the System.Diagnostics.* calls. Why is that?
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How do I revert all local changes in Git managed project to previous state?
...everal commits, I did git status which told me everything was up to date and there were no local changes.
14 Answers
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What is an idempotent operation?
...g that x in the mathematical definition represents the state of an object, and f is an operation that may mutate that object. For example, consider the Python set and its discard method. The discard method removes an element from a set, and does nothing if the element does not exist. So:
my_set.dis...
How does Facebook Sharer select Images and other metadata when sharing my URL?
...rom the source as a preview for their link. How are these images selected, and how can I ensure that any particular image on my page is always included in this list?
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ISO time (ISO 8601) in Python
I have a file. In Python, I would like to take its creation time, and convert it to an ISO time (ISO 8601) string while preserving the fact that it was created in the Eastern Time Zone (ET) .
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Display number with leading zeros
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In Python 2 (and Python 3) you can do:
print "%02d" % (1,)
Basically % is like printf or sprintf (see docs).
For Python 3.+, the same behavior can also be achieved with format:
print("{:02d}".format(1))
For Python 3.6+ the same...
Should I use char** argv or char* argv[]?
I'm just learning C and was wondering which one of these I should use in my main method. Is there any difference? Which one is more common?
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In Swift how to call method with parameters on GCD main thread?
In my app I have a function that makes an NSRURLSession and sends out an NSURLRequest using
9 Answers
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