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  Select top 3 values from each group in a table with SQL

Yesterday, my friend Liu Bing asked me a question about how to select top 3 values for each person in a database table using SQL. I think this question is interesting and it deserves some thoughts. Here I record down how to solve this issue. Assume we have a table which has two columns, one column contains the names of some people and the other column contains some values related to each person. One person can have more than one value. Each value has a numeric type. The question is we want to se...

   SQL,Correlated query,top 3     2013-05-23 03:21:25

  PHP buffer: output_buffering and ob_start

buffer is one piece of memory section, it is usually 4Kb in Linux. It is mainly used between different devices with different speed or different priorities. With buffer, the waiting time between different processes will be reduced. Here is one simple example, when you type something in a text editor, every time when you type a character, the operating system will not write it to the disk directly, instead it will write it to buffer first When the buffer is full, the data in the buffer will be wr...

   PHP buffer,output_buffering,ob_start     2013-06-20 22:54:15

  Understanding the "this" keyword in JavaScript

Many people get tripped up by the this keyword in JavaScript. I think the confusion comes from people reasonably expecting this to work like “this” does in Java or the way people use “self” in Python. Although this is sometimes used to similar effect, it’s nothing like “this” in Java or other languages. And while it’s a little harder to understand, its behavior isn’t magic. In fact, this follows a relatively small set of simple rules. This...

   JavaScript,this,understanding     2012-03-29 13:48:59

  Be Aware of these 10 mistakes while designing Your Mobile App!

So you have finally decided to enter the world of technology and you are going to design an application for your business. The time has become when you have to give all the nitty-gitty grins a look and design your own mobile app for promoting your business online. Well when you have finally decided to design your mobile application, here are some mistakes that you are not allowed to make. Have a look:   Do Not Start Designing Your App Without Wireframes Normal 0 false ...

       2014-12-11 02:12:02

  Kubernetes Authentication & Authorization 101

If we want to build a system with user modules, Authentication and Authorization are something that we can never ignore, though they could be fuzzy to understand. Authentication (from Greek: αὐθεντικÏŒς authentikos, “real, genuine”, from αὐθέντης authentes, “author”) is the act of proving an assertion, such as the identity of a computer s...

   RBAC,AUTHORIZATION,AUTHENTICATION,KUBERNETES     2021-06-05 23:19:18

  Top Ten Tips for Correct C++ Coding

Brian Overland, long-time Microsoft veteran and author of C++ Without Fear: A Beginner's Guide That Makes You Feel Smart, 2nd Edition, shares 10 of his most hard-earned, time-saving insights from decades of writing and debugging C++ code.My first introduction to the C family of languages was decades ago (yes, I know this dates me horribly). Later I learned C++. I wish someone back then had steered me around the most obvious potholes; it might have saved me hundreds of frustrating hours.I ca...

   C++,Tips,Top,Ten,Magic number,Integer di     2011-09-03 10:58:35

  Currying in Python

What is Currying? Currying is like a kind of incremental binding of function arguments. Let’s define a simple function which takes 5 arguments: 1def f(a, b, c, d, e):2    print(a, b, c, d, e) In a language where currying is supported, f is a function which takes one argument (a) and returns a function which takes 4 arguments. This means that f(5) is the following function: 1def g(b, c, d, e):2    f(5, b, c, d, e) We could emulate this behavior the...

   Python,Curring,Binding,Implement     2012-03-19 12:59:10

  The 15 Golden Rules of UI design and flow.

Last night a good friend of mine showed me the latest Need for Speed game on the iphone / ipad. Quite an impressive feat of rendering and a relatively good game to boot. However, the front end, wow, a classic case in UI mis-engineering. Loads of stats, pages and pages of bits and pieces to wade through – a classic case of over stimulating the player with lots of decisions they have no business making – stuff that will significantly change their game play experience but being...

   UI design,Game design,Feature     2012-04-05 12:20:18

  Pointers, arrays, and string literals

A recently posted question on Stack Overflow highlighted a common misconception about the role of pointers and arrays held by many programmers learning C.The confusion stems from a misunderstanding concerning the role of pointers and strings in C. A pointer is an address in memory. It often points to an index in an array, such as in the function strtoupper in the following code:void strtoupper(char *str) { if (str) { // null ptr check, courtesy of Michael while (...

   char pointer,initialization,literal,cann     2011-09-22 13:29:23

  Diving Deeper into HTML5 Offline Browsing

Recently, I published an article on one of the new features in HTML 5 called Offline Browsing  in HTML5 with ApplicationCache.The response to that article was good, and I was asked to expand on some further points including:how to decide on what files to cachethe implications of caching those filesdebugging the ApplicationCacheSo, that’s where this article will start: where the last one finished.  If you haven’t, you should probably read the previous article before this o...

   HTML5,Offline browsing,New breakthrough,Feature     2011-12-20 08:46:06