大约有 47,000 项符合查询结果（耗时：0.0494秒） [XML]
Select n random rows from SQL Server table
...th about 50,000 rows in it. I want to select about 5,000 of those rows at random. I've thought of a complicated way, creating a temp table with a "random number" column, copying my table into that, looping through the temp table and updating each row with RAND() , and then selecting from that table...
Building executable jar with maven?
...6: someone fixed it, this answer refers to the version preceding the edit) and this explains, at least partially, why you run into troubles.
It generates two jar files in logmanager/target: logmanager-0.1.0.jar, and logmanager-0.1.0-jar-with-dependencies.jar.
The first one is the JAR of the logma...
&& (AND) and || (OR) in IF statements
...
No, it will not be evaluated. And this is very useful. For example, if you need to test whether a String is not null or empty, you can write:
if (str != null && !str.isEmpty()) {
doSomethingWith(str.charAt(0));
}
or, the other way around
if ...
Object comparison in JavaScript [duplicate]
...
Unfortunately there is no perfect way, unless you use _proto_ recursively and access all non-enumerable properties, but this works in Firefox only.
So the best I can do is to guess usage scenarios.
1) Fast and limited.
Works when you have simple JSON-style objects without methods and DOM nodes...
MySQL vs MongoDB 1000 reads
I have been very excited about MongoDb and have been testing it lately. I had a table called posts in MySQL with about 20 million records indexed only on a field called 'id'.
...
“CAUTION: provisional headers are shown” in Chrome debugger
...r Latest Versions of chrome
Type chrome://net-export/ in the address bar and hit enter.
Start Recording. And save Recording file to local.
Open the page that is showing problems.
Go back to net-internals
You can view Recorded Log file Here https://netlog-viewer.appspot.com/#import
click on events ...
Can I store the .git folder outside the files I want tracked?
...e git as a backup system. So let's say I have a directory ./backup/myfiles and I want to back that up using git. To keep things clean I don't want to have a .git directory in the myfiles folder, so I thought I could create ./backup/git_repos/myfiles. From looking at the git docs, I've tried doing th...
maximum value of int
...
in C99 you can also use UINT64_MAX and INT64_MAX
– Dmitry Vyal
Oct 2 '13 at 9:08
3
...
How to benchmark efficiency of PHP script
...
If you actually want to benchmark real world code, use tools like Xdebug and XHProf.
Xdebug is great for when you're working in dev/staging, and XHProf is a great tool for production and it's safe to run it there (as long as you read the instructions). The results of any one single page load aren...
What's the best way to set a single pixel in an HTML5 canvas?
...
There are two best contenders:
Create a 1×1 image data, set the color, and putImageData at the location:
var id = myContext.createImageData(1,1); // only do this once per page
var d = id.data; // only do this once per page
d[0] = r;
d[1] = g;
d[2] = b;
d[3] = a;
...