大约有 40,000 项符合查询结果（耗时：0.0364秒） [XML]
Select n random rows from SQL Server table
...the key scan of values plus the join cost, which on a large table with a small percentage selection should be reasonable.
share
|
improve this answer
|
follow
...
What is the difference between task and thread?
...y only use them if you want to run multiple heavy computations on multiple CPUs. For example, in Windows, a thread weighs 12 KiByte (I think), in Linux, a thread weighs as little as 4 KiByte, in Erlang/BEAM even just 400 Byte. In .NET, it's 1 MiByte!)
...
What is “thread local storage” in Python, and why do I need it?
In Python specifically, how do variables get shared between threads?
5 Answers
5
...
When to use enumerateObjectsUsingBlock vs. for
...
Ultimately, use whichever pattern you want to use and comes more naturally in the context.
While for(... in ...) is quite convenient and syntactically brief, enumerateObjectsUsingBlock: has a number of features that may or may not prove interesting:
enumerateObjectsUsingBlock: will be as fas...
How expensive is the lock statement?
I've been experimenting with multi threading and parallel processing and I needed a counter to do some basic counting and statistic analysis of the speed of the processing. To avoid problems with concurrent use of my class I've used a lock statement on a private variable in my class:
...
download and install visual studio 2008 [closed]
... 2003, Windows Server 2008, Windows Vista, Windows XP
Minimum: 1.6 GHz CPU, 384 MB RAM, 1024x768 display, 5400 RPM hard disk
Recommended: 2.2 GHz or higher CPU, 1024 MB or more RAM, 1280x1024 display, 7200 RPM or higher hard disk
On Windows Vista: 2.4 GHz CPU, 768 MB RAM
Maintain Int...
从 !important 到关于叹号的 !一切 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...的人当然不只我一个，stackoverflow 上有个人也提了类似的问题：“为什么 CSS 和 C-based （的）语言中叹号的涵义相反？”他还问道：“除了 CSS，还有什么语言是用叹号表达肯定而非否定的呢？”（随后有人提醒他，自然语言就是...
30岁之后，程序员该向什么方向发展？ - 杂谈 - 清泛网 - 专注C/C++及内核技术
...，脑袋没有那么灵光，没有那么有冲劲了，这也是个人的问题。如果你自己不努力，到多少岁都一样。
以前也有人问我二十几岁再开始编程晚不晚，我的回答是，不晚，什么时候都不晚。
QA&2. 您个人或身边有这样的实例吗？...
Remove spaces from std::string in C++
... preferred way to remove spaces from a string in C++? I could loop through all the characters and build a new string, but is there a better way?
...
Should I use multiplication or division?
...wer compared to the lower overhead of the VM. Remember that compilers generally cannot optimize floating point much in order to guarantee precision.
– rasmus
Sep 14 '12 at 7:22
7
...