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GROUP_CONCAT ORDER BY
...
You can use ORDER BY inside the GROUP_CONCAT function in this way:
SELECT li.client_id, group_concat(li.percentage ORDER BY li.views ASC) AS views,
group_concat(li.percentage ORDER BY li.percentage ASC)
FROM li GROUP BY client_id
...
What is more efficient? Using pow to square or just multiply it with itself?
...d::chrono::high_resolution_clock::time_point from;
};
int main (int argc, char* argv[])
{
double total;
Timer timer;
total = 0.0;
timer.start();
for (double i = 0.0; i < 1.0; i += 1e-8)
total += std::pow (i,2);
std::cout << "std::pow(i,2): " << timer.elapsed() <...
What does an Asterisk (*) do in a CSS selector?
...
It is a wildcard, this means it will select all elements within that portion of the DOM.
For example, if I want apply margin to every element on my entire page you can use:
* {
margin: 10px;
}
You can also use this within sub-selections, for example the ...
When and why are database joins expensive?
...s back to mitigating the size of the working set. Joins involving properly selected keys with correctly set up indexes are cheap, not expensive, because they allow significant pruning of the result before the rows are materialised.
Materialising the result involves bulk disk reads which are the mo...
Manually put files to Android emulator SD card
... Card through the Android Perspective (it is called DDMS in Eclipse). Just select the Emulator in the left part of the screen and then choose the File Explorer tab. Above the list with your files should be two symbols, one with an arrow pointing at a phone, clicking this will allow you to choose a f...
Failed to build gem native extension (installing Compass)
...l the Xcode Command Line Tools this is the key to install Compass.
xcode-select --install
Installing the Xcode Command Line Tools are the key to getting Compass working on OS X
3. Install Compass
sudo gem install compass
...
How to get TimeZone from android mobile?
...ndar.getInstance();
TimeZone tz = cal.getTimeZone();
It will return user selected timezone.
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Webstorm: “Cannot Resolve Directory”
...t directory as a Resource. To do this, go to Settings > Directories and select your asset root folder from the right-hand panel. Then mark it as Resource Root by clicking the button above the file browser.
From the Jetbrains documentation, a Resource Root enables WebStorm to complete relative pa...
“Unable to find manifest signing certificate in the certificate store” - even when add new key
...t click on your project
click on properties
usually on the left-hand side, select the "Signing" tab
check off the Sign the ClickOnce manifests
Make sure you save!
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What is the meaning of the term arena in relation to memory?
... manage memory manually by handing out parts of that memory. For example:
char * arena = malloc(HUGE_NUMBER);
unsigned int current = 0;
void * my_malloc(size_t n) { current += n; return arena + current - n; }
The point is that you get full control over how the memory allocation works. The only ...