大约有 40,000 项符合查询结果（耗时：0.0557秒） [XML]
MySQL indexes - what are the best practices?
I've been using indexes on my MySQL databases for a while now but never properly learnt about them. Generally I put an index on any fields that I will be searching or selecting using a WHERE clause but sometimes it doesn't seem so black and white.
...
#ifdef replacement in the Swift language
...u can still use the "#if/#else/#endif" preprocessor macros (although more constrained), as per Apple docs. Here's an example:
#if DEBUG
let a = 2
#else
let a = 3
#endif
Now, you must set the "DEBUG" symbol elsewhere, though. Set it in the "Swift Compiler - Custom Flags" section, "Other Sw...
How do I get Flask to run on port 80?
...
So it's throwing up that error message because you have apache2 running on port 80.
If this is for development, I would just leave it as it is on port 5000.
If it's for production either:
Not Recommended
Stop apache2 first;
Not recommended as it states in the documentation:
You can us...
Take screenshots in the iOS simulator
I want to take a screenshot of my iOS application when it is running in the simulator, and save the screenshot on my Mac. How can I do this?
...
Check if an apt-get package is installed and then install it if it's not on Linux
I'm working on a Ubuntu system and currently this is what I'm doing:
22 Answers
22
...
Ruby on Rails Callback, what is difference between :before_save and :before_create?
...ld you explain in detail what the :before_save and :before_create Ruby on Rails callbacks are, and what they have to do with Rails validations? Does validation occur after :before_save or :before_create ?
...
CRON job to run on the last day of the month
I need to create a CRON job that will run on the last day of every month.
I will create it using cPanel.
15 Answers
...
Git Bash is extremely slow on Windows 7 x64
I've been using Git on both Windows and Ubuntu during the development of a small project, frequently flipping back and forth between the two. The issue is that Git Bash consistently becomes slow.
...
Get the device width in javascript
....
Sometimes it's also useful to use window.innerWidth (not typically found on mobile devices) instead of screen width when dealing with desktop browsers where the window size is often less than the device screen size.
Typically, when dealing with mobile devices AND desktop browsers I use the follow...
Different floating point result with optimization enabled - compiler bug?
The below code works on Visual Studio 2008 with and without optimization. But it only works on g++ without optimization (O0).
...