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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

  Why localStorage only allows to store string values

localStorage allows data to be stored in browsers across sessions, the data will be there even though the session is expired. It is frequently used to store static data so that they can be loaded when needed. But as per spec, it says that the keys and the values are always strings (note that, as with objects, integer keys will be automatically converted to strings). Why cannot store the object as it is? Take a look at an example: var str = "test"; localStorage.setItem("str", str); cons...

   JAVASCRIPT,LOCALSTORAGE     2020-04-05 00:54:29

  Everything you need to know about what happened at Apple’s Special Event 2019

Apple’s special event that was announced in mid-November is finally over. The company held a presentation event in New York City where it highlighted the best apps and games of 2019 with no new software or hardware announcements at all.   On the event, five different nominations were announced: Apple’s chosen favourite apps, top free apps, top paid apps, top free games, and top paid games for 2019. Usual keynotes from Apple The tech industry is pretty accustomed to Apple’s...

   APPLE,EVENTS     2019-12-04 05:50:15

  6 Promising Ways by Which You Can Enhance the App Testing Process

Now mobile application industry is exploding with application demands more than ever. According to the latest mobile app technology news the integration of mobile application service with enterprise business is main cause app developing companies are booming. But with this tremendous demands, competition heats up in market and clients are impatient to get the results.   This pressure of a deadline and impatient client,  most times becomes a burden to the developing and QA departm...

   TECHNOLOGY,MOBILE APP,APP DEVELOPMENT,APP TESTING,MOBILE APP TESTING     2017-04-17 08:02:07

  Shortest command on Linux

Usually when we log in to a Linux system,. we may type some frequently used Linux commands such as pwd,ls, ps etc. All these commands are really simple but powerful with different options. But do you know what is the shortest command on Linux? The answer is w. According to Linux manual, w will show who is logged on and what they are doing on the system. w displays information about the users currently on the machine, and their processes. The header shows, in this order, the current time, how l...

   Linux,w,shortest command     2014-04-30 11:07:38

  Revolutionize Your Event Planning with Interactive Presentation Templates

Making a plan for a successful event requires a lot more than just booking a place and sending out invitations. To truly catch your audience’s heart and ensure a memorable experience, you need to think outside of old-school presentations. One effective way to uplift your event is by using interactive elements in the presentation.  The Power of Interactive Presentations Such presentations are made to engage and involve the crowd actively. They won’t just be presenting info passiv...

   EVENT PLANNING     2024-08-29 01:23:53

  What is pjax and why we should use it?

What is pjax? Now many websites such as Facebook, Twitter support one browsing style which is when you click one link on their sites, the page will not be redirected, instead only the page contents are updated and URL on address bar is changed. This kind of user experience is much better compared to load the whole page with a blink. There is one important component in the above browsing experience, these websites' AJAX refresh support browser history, when refreshing the page, the address on the...

   pjax,AJAX,history     2013-04-23 12:22:37

  Use pdb to help understand python program

  As I have mentioned in Why do I need a debugger?: (3) Debugger is a good tool to help you understand code. So when I come across difficulty to understand vfscount.py code in bcc project, I know it is time to resort to pdb, python's debugger, to help me. The thing which confuses me is here: counts = b.get_table("counts") for k, v in sorted(counts.items(), key=lambda counts: counts[1].value): print("%-16x %-26s %8d" % (k.ip, b.ksym(k.ip), v.val...

       2017-08-22 22:42:37

  The basics of Client/Server socket programming

  While Client/Server communication model is ubiquitous nowadays, most of them involve socket programming knowledge. In this post, I will introduce some rudimentary aspects of it: (1) Short/Long-lived TCP connection.Short-lived TCP connection refers to following pattern: Client creates a connection to server; send message, then close the connection. If Client wants to transmit information again, repeat the above steps. Because establishing and destroying TCP s...

       2017-09-26 19:43:10

  Microsoft is filing a new patent about transparent display

Microsoft is filing a new patent about transparent display screen, it may be used on augmented reality technologies of tablets, phones and laptops. Similar to the scenes in the movie Minority Report. Minority Report was showed in 2002, it described a world of 2054, at that time 3D technology is mature. But after 10 years of this movie, Microsoft not only invented the basis of this technology, but also make it more portable.Patent Bolt recently revealed a patent application of Microsoft about tra...

   Microsoft,Transparent display,3D,Patent     2012-05-10 05:31:16

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