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  <=> operator in MySQL


Have you ever seen "<=>" in a SQL query while using MySQL? Does it mean less and equals to and greater than? Actually if you consider it as the union of <= and =>, great, you are close to it. This is one form of equal operator in MySQL, it has the similar meaning to the = operator with some subtle difference. According to MySQL documentation, <=> is NULL-safe equal. This operator performs an equality comparison like the = operator, but returns 1 rather than NULL if both operand...

   MySQL,NULL safe,<=>     2014-03-24 06:23:22


  How regular expression works


Rob Pike wrote 30 lines of codes to realize a simple regular expression matcher in his book The practice of Programming. This piece of code is really cool. Let's take a look at the code.Meaning of different characters.Character Meaning c General character . Match any single character ^ Match start of a string $ Match end of a string * Match zero or many occurrences of a character /*match :Test the regexp in text*/int match(char* regexp,char* text){    if(regexp[0] == '^') ...

   Regular expression,Implementation,Rob Pike,C     2012-06-25 05:23:41


  10 principles to start your own business


Guy Kawasaki is a Silicon Valley venture capitalist, bestselling author, and Apple Fellow. He was one of the Apple employees originally responsible for marketing the Macintosh in 1984. He is currently a Managing Director of Garage Technology Ventures, and has been involved in the rumor reporting site Truemors and the RSS aggregation Alltop. He is also a well-known blogger.We summarized 10 principles to start a new business from one of his presentations. 1. Make meaning in your companyThe most...

   Business,Guy Kawasaki,Tips     2012-05-18 12:11:20


  Removing duplicates in sql


In modern web development, it’s standard practice to make use of a database abstraction layer, typically an Object-Relational Mapper based on either the Active Record pattern or the Data Mapper pattern. There are several pros and cons to this which are fairly well established, so I’ll spare us all from enumerating them all right now. One established pro worth mentioning is that these systems typically provide a high level interface for fetching data, often removing the need to ‘hand wr...

   SQL,Duplicate,Remove,Web design     2012-01-05 08:20:13


  Difference between sans-serif and serif font


When we design website, we will often need to choose which font to use while displaying contents on the page. Basically what's the criteria for the choice? There are two big families of fonts : sans-serif and serif. We need to first understand what the difference is between these two. The word sans is from French, the meaning of it is without. So the difference between sans-serif and serif is serif font will have lines in all ends of the character while sans-serif fonts don't have. Some examples...

   Sans-serif,Serif,French     2013-06-10 05:11:57


  3 meanings of Stack


We may frequently see stack when we read programming books. But many times we may be confused about the different meanings of it. This term actually has three common meanings. Here we explain the three different meanings of Stack in programming. 1. Data structure The first meaning of Stack defines a method for storing data. Its feature is LIFO9Last In First Out). In this data structure, data are accumulated level by level. The data last put in is added at the top of the stack. When using the dat...

   Stack,Memory,Data structure     2014-02-24 04:56:46


  The worst program I ever worked on


Most contract jobs fade pretty quickly in memory after the work is done, but some you remember for the rest of your life. This is one of the latter variety. This happened long ago, at a (fair sized) company that shall remain nameless. The software was a chunk of code that had been maintained by a single guy that had been fired recently and was a core component of a commercial system. So far nothing unusual, companies tend to find out that they have a piece of critical knowledge in one head all ...

   Program,worst     2011-03-17 13:58:36


  Revenue = X


We've been experimenting with app prices for quite some time and again and again we've noticed a funny effect:No matter what price we choose, we always make the same revenue.I attached two charts to illustrate that. I recently lowered the price of the iPad app (http://bit.ly/92xWv1) from 5 to 1 Dollars. At first the sales spike, then they even out to previous levels. Meaning: By cutting the price by factor 5, I am selling exactly 5 x more apps. Then we lowered the price of iA Writer for Mac...

   Revenue,Price,Productivity,Investment,Discount,Software     2011-11-17 02:31:58


  Create namespace in JavaScript


A namespace (sometimes also called a name scope) is an abstract container or environment created to hold a logical grouping of unique identifiers or symbols (i.e., names). An identifier defined in a namespace is associated only with that namespace. The same identifier can be independently defined in multiple namespaces. That is, the meaning associated with an identifier defined in one namespace may or may not have the same meaning as the same identifier defined in another namespace. Languag...

   JavaScript,namespace,example     2012-05-10 04:57:17


  Understanding abstract interface in Java


Have you read about an interface declaration as public abstract interface InterfaceName in Java? At the first glance, is it a weird declaration? Why should we declare an interface as abstract? For example, we may see below code in some projects: public abstract interface MyInterface { public void check(); public abstract boolean check(boolean really); } Actually here abstract is redundant, an interface is implicitly abstract, we no need to put an abstract in front of interface. But it do...

   Java,abstract interface     2014-08-18 23:07:27