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SEARCH KEYWORD -- Column oriented

  Why should we keep column as NOT NULL instead of NULL in MySQL?

Keep table column as NOT NULL instead of NULL except in some special cases. This statement is cited by many articles of MySQL optimization, but they don't say why we should do this. Here we discuss about this. First why are there many people using NULL when defining table? The reasons may be: NULL the the default when defining table, the rookies or people who don't want to have much troubles will keep this default setting Many people think NOT NULL will require more space Many people don't want...

   MySQL,NULL,reason     2012-10-27 03:21:27

  Why are column oriented databases so much faster than row oriented databases?

I have been playing around with Hybrid Word Aligned Bitmaps for a few weeks now, and they turn out to be a rather remarkable data structure.  I believe that they are utilized extensively in modern column oriented databases such as Vertica and MonetDB. Essentially HWABs are a data structure that allows you to represent a sparse bitmap (series of 0's and 1's) really efficiently in memory.  The key trick here is the use of run length encoding to compress the bitmap into fe...

   Database,Column oriented,Speed analysis,Vertica     2012-01-29 04:27:05

  Inline IF and CASE statements in MySQL

There are times where running IF statements inside a query can be useful. MySQL provides a simple way to do this through the use of IF and CASE statements. The IF statement takes three arguments; the conditional, the true value and the false value. False and true values may be static values or column values. For example: SELECT IF(score > 100, 100, score) AS score FROM exam_results this will return the value in the score column limited to a maximum value of 100. IF statements can a...

   MySQK,IF,Condition,CASE,SQL     2012-04-22 10:37:01

  Relationship oriented website vs content oriented website

Relationship oriented website is a kind of website based on friend circle, people come to the website to share news with their friends and see what's happening around their friends, these websites include Facebook, Twitter and Tumblr. While content oriented website is a kind of website based on unique content, people come to the website to find information or find answers for their questions, these websites include TechCrunch, The Verge and Medium. Most of websites on the Internet nowadays belon...

   Relationship oriented,Content oriented, Loyalty     2013-07-11 09:20:37

  CASSANDRA data model

Cassandra is an open source distributed database, it combines dynamic key/value and column oriented feature of Bigtable. Features of Cassandra are: Flexible schema, no need to design schema first, it's very convenient to add or delete strings Support range search on keys High usability, extensible. The single node error will not affect the cluster. We can think Cassandra's data model as a 4 or 5 dimensional Hash. COLUMN Columns is the smallest data unit in Cassandra, it is a 3 dimensional data...

   Cassandra,database,sort     2013-06-08 22:07:40

  Objective-C Is The Language

My good friend Brent Simmons invokes a historical email from Linus Torvalds, about his disdain for C++C++ is a horrible language. It’s made more horrible by the fact that a lot of substandard programmers use it, to the point where it’s much much easier to generate total and utter crap with it.Brent affirms his support while paying homage to plain-old C:But I will admit to an enduring love of C. I still think of C not as C but as the language.I loved C. Emphasis on the past-tense. A...

   Objective-C,C,Apple,OOP,C++     2011-11-07 08:23:08

  Macro to change text color conditionally in Excel

Macros are small but very powerful VBA programs in Microsoft Office software. They can help us complete some repeated tasks automatically. Today, I will show you one macro example which is to change the text color conditionally. The excel file has a work sheet which contains some records of request. I want to check the status of each request, if the status of a request is approved, the text color of the status should be green; if the status of a request is rejected, the text color of the status ...

   Macro,Excel,Text color,Conditionally     2012-07-07 12:53:28

  Understanding Twitter Bootstrap 3

On 27, July, Twitter Bootstrap 3 RC 1 was released, if there are no major bugs found in this release, then it will be the final released Twitter Bootstrap 3 with some minor changes. What changes does Bootstrap 3 have compared to Bootstrap 2? After checking the documents, we can find that there are mainly 3 changes. Embrace flat design In Bootstrap 3, it begins to embrace flat design. First from the official webpage of Bootstrap 3, we can find elements are flat designed. Also, all buttons have no...

   Bootstrap 3,Change,Bootstrap 2     2013-08-05 07:06:22

  C++, Ruby and CoffeeScript complexity comparison

There are many programming languages around the world, they all designed to help programmer solve some problems, finish some tasks. These languages are often divided into different types, there are structural, object-oriented, functional, scripting languages etc. Some are easy to pick up such as Java, while some are thought to be difficult to learn such as C++. So how do we understand complexities of different programming languages?Many people agree that C++ is very complex languages, it has poi...

   Complexity, languages, C++,Ruby,CoffeeScript     2012-06-12 04:46:01

  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

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