SEARCH KEYWORD -- SECONDARY INDEX
How MySQL optmizes ORDER BY
In some situations, MySQL will just use an index to fulfill the requirement of an ORDER BY or GROUP BY statement without extra sorting. Although ORDER BY will not have the exact match with index, index can still be used as long as the portion that is not included in the index is included in the where clause. The following queries will all use index to process the ORDER BY or GROUP BY part: SELECT * FROM t1 ORDER BY key_part1,key_part2,... ;SELECT * FROM t1 WHERE key_part1=constant ORDER BY key_p...
MySQL,index,ORDER BY,optimization 2012-11-13 11:01:05
MySQL Index Merge Optimization Practices
In production environment databases, it is often seen that some SQL where conditions include: equal condition on a normal index + primary key range query + order by limit Although using a normal index would be more efficient, the system chooses to use index merge instead in some cases. This article explores such index merge situations. Index Merge Official Introduction The Index Merge access method retrieves rows with multiple range scans and merges their results into one. Generall...
INDEX MERGE,MYSQL,PRIMARY INDEX,SECONDARY INDEX 2024-09-10 04:52:26
Read 10 new books from O'Reilly for free
Recently O'Reilly provided free access to some books. Some of them are even in early release status. Here we recommend 10 of them. 1ã€Mastering Perl 2ã€Git Pocket Guide 3ã€Vagrant: Up and Running 4ã€High Performance Browser Networking 5ã€802.11ac: A Survival Guide 6ã€Test-Driven Development with Python 7ã€Interactive Data Visualization for the Web 8ã€HTML5 Canvas 9ã€Programming JavaScript Applications 10ã€Agile Data Source : http://linu...
O'Reilly,Free book,Early release 2013-07-03 07:56:20
TIOBE : Objective-C overtakes C++
TIOBE recently released the programming community index for July. From the index,we can find that the biggest change is that Objective-C overtakes C++ as the 3rd most popular language among programmers. Because of the popularity of iPhone and iPad, Objective-C is used by more and more mobile developers who want to develop apps for Apple products. Also, many developers are willing to develop apps for Apple since they can gain more profit on Apple platform than on Android platform.C++ is mainly us...
TIOBE,July,C++,Objective-C,overtake 2012-07-05 22:49:49
JavaScript: Private variables
The first thing you often hear when talking about JavaScript is often “JavaScript doesn’t have visibility modifiers, hence it doesn’t support private variables”. This is only valid for 50%, because JavaScript indeed doesn’t have visibility modifiers (public, private, friend) but it has closures and function scopes. With these tools we can make variables private. Let’s take the following function: var names = ["Kenneth", "John", "Marc", "Robert"]; var lookup =...
JavaScript,private variable,closure 2012-04-28 11:46:34
TIOBE : C overtakes Java as the No.1 programming language
TIOBE has released the Programming Community Index for April 2012. The highlight of this month is that C overtakes Java as the No.1 programming language again. C language is liked by more and more developers of all ages. Due to the growing popularity of the Android platform, Java decline will not be obvious. Previously Java took a very long time to overtake C, now C once again returns to the throne. The battle between these two languages will continue.The top three are respectively, C, Jav...
TIOBE : Where is that next big programming language?
TIOBE has released the Programming Community Index for May 2012 a bit late. The top 3 languages do not change compared to last Month TIOBE : C overtakes Java as the No.1 programming language, they are still C,Java and C++. However, the share of Java is continuing dropping, Objective-C is steadily rising Other languages which have rising trend are Visual Basic.NET,PL/SQL and Logo.The last 8 years not much has changed in the top 10 of the TIOBE index except for Objective-C (in) and Del...
TIOBE : What's the future of C#?
TIOBE released the programming language index for August 2012, the top 3 programming languages are still C, Java and Objective-C. Objective-C still performs well after it ranked 3rd place last month, it's still rising. Is there any possibilty Object-C will overtake Java in the near future? However, Microsoft's C# doesn't look so good. C# is generally recognized as the enterprise language with most modern and expressive features available today and C# has shown more downward trends in the past an...
Sort an array with only one local variable
Array sorting algorithm question is frequently asked during technical interviews. There are lots of sort algorithms including bubble sort, selection sort, insertion sort, quick sort, merge sort etc. Usually interviewees will be asked to implement sort algorithms. But have you ever been asked to sort an array which you are allowed to define ONLY ONE local variable in your algorithm? Bubble sort can be used to do this actually. Normally a bubble sort algorithm may need three local ...
JAVASCRIPT,ALGORITHM,SORTING,BUBBLE SORT 2016-10-07 09:46:49
Can a == true && a == false be true in JavaScript?
JavaScript is a weak typed language and it has a loose comparison feature where two objects/values of different type can be compared using == operator. This provides developers great flexibility and confusion at the same time. Before understanding how == works in JavaScript, can you first answer the question in the post title? Can a == true && a == false be true in JavaScript? Normally, we would think that this expression will always return false since a can be either true or ...
JAVASCRIPT,COMPARISON,INTERVIEW QUESTION,== 2018-03-25 03:39:43
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