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what circumstances are indexes, but not used?Indexes do not always take effect, such as the following, which will invalidate the index : If there is or in the condition, even if some of the conditions in the index are not used ( which is why the use of or is minimized ), in the example user_id no index

interfaces that do not inherit or implement any other Java framework. Here is a quote from Martin Fowler personal website: "We wondered why people were so against using regular objects on their systems and concluded that it is because simple OB Jects lacked a fancy name. So we gave them one, and it's caught on very nicely. " --martin FowlerWe wondered why people did not like to use ordinary o

What is the function of zoom: 1 in CSS? What is the function of CSS zoom? What is the role of zoom: 1 in CSS:Suggestion: writing code as much as possible can effectively improve learning efficiency and depth.The zoom attribute

I/O instead of sequential I/O, which makes accessing index pages slower. So what is the ideal filling factor? It relies on the application's ratio of read and write to SQL Server tables. As a first principle, follow the guidelines below: low-change tables (read-write ratios of 100:1): 100% higher fill factor for changed tables (write over Read): 50-70% fill factor reads and writes in half: 80-90% 's fill f

Just like what is the difference between the following code {code...} and {code? Humbly ask the experts for advice, just like The following code Echo 'configuration error'; exit (3); // Status 3 indicates exit due to configuration error And // Exit directly ('configuration error '); What is the difference? I would lik

What this article brings to you is about what is BFC? What is the use of BFC in CSS? , there is a certain reference value, the need for friends can refer to, I hope you have some help.

Insist ~ insist ~ insist ~! Sweet Tooth Like to eat sweets What should we get for dessert? What do we have for dessert? We just finished eating dinner! And you ' re already thinking about dessert!? We've just had dinner, and you've been thinking about dessert? Sorry.i have such a huge sweet tooth! I love dessert. I'm sorr

JQuery1.3.2 source code learning This source code uses the current jQuery 1.3.2 version. download time:. Click here to download A function 1 /*! 2 * jQuery JavaScript Library v1.3.2 3 * http://jquery.com/ 4 * 5 * Copyright (c) 2009 John Resig 6 * Dual licensed under the MIT and GPL licenses. 7 * http://docs.jquery.com/License 8 * 9 * Date: 17:34:21-0500 (Thu, 19 Feb 2009) 10 * Revision: 6246 11 */ 12 (function (){ 4376 })(); If you omit the content in the middle, you can see lines 12th to 4376.

Php is also a bit time-consuming. reading some technical blogs often tells us about lua. under what circumstances will lua be used? Do you need to be skilled in using it? I want to know if phper needs to understand lua. it may take some time to engage in php. I read some technical blogs and often see people talking about lua. under what circumstances will lua be

What is persistent connection and what is short connection?Post a classic post. After reading it, there should be no problem: Diversity of TCP/IP communication program design People who are new to TCP/IP communication design can quickly compile a communication program based on the example.According to this, some peopl

)This is the magic of data structures.So what is an algorithm? This can only be forced to continue the analogy. I want to learn Kung fu. After I entered the book Room of martial Arts cheats, I ran out with a lot of books. Open a look, there is a dragon 18 palm, nine Yin Canon, nine Yang Martial, easy to warp, the unive

What is polymorphism. Concept: The same operation acts on different objects, can have different interpretations, produce different execution results, this is polymorphism. Simply put: the reference to the base class refers to the object of the subclass. Why use polymorphism? Reason: We know that encapsulation can hide implementation details, making code modular,

. Maybe you are a friend of an object just like an object. Don't get dizzy with the concept. Give you a column, if you want to buy several assembled PCs in Zhongguancun, what do you do when you get there? Are the installation engineers sitting with you, complete an installation configuration sheet with the information you provide. This configuration sheet can be imagined as a class, and it is a piece of pap

(Ob1 is OB2) equivalent to (ID (ob1) = = ID (ob2)) First the ID function can get the memory address of the object, if the memory address of the two objects is the same, then the two objects must be an object. is equivalent to IS. Python source code is proof. Static Pyobject

What is LinuxThe same set of operating systems cannot be run on a platform of different architectures.Refer to the HARDWARE function function and modify your operating system program code, the revised operating system will be able to run on another hardware platform. This is the software migration .Linux is an open-sou

What information does the Singapore non-profit organization foundation need to register? Registration requirements ,?? Time, cost, and process?The Singapore non-profit organization foundation is registered with the Singapore accounting and Enterprise Development Board (ACRA) for public company limited by guarantee ). Non-profit organizations do not have registered funds and do not have to pay taxes. Therefo

Medical University, China and formulated the Chinese norm. We are now able to look up children aged 6-16 and adults over 16 years old. Through psychological attention, you can understand your intelligence level and potential, identify the damage caused by traffic accidents, and provide scientific evidence to give full play to your own advantages, scientifically fill in the college entrance examination volunteers, and offer superior health and education. The IQ test contains eleven projects, in

What is EF? (EF basic series 2) What is ef?Background of EF: Write ADO. NET data access code is dull and boring, so Microsoft provides an object relationship ing framework (EF ), EF can automatically help our program to generate related database activities. Definition of EF:

You want to know why so many services are running. You browsed the task manager and saw two media players (Windows Media Player... however, you are not using a media player. what is it? It is not like a process that occupies a lot of memory... I am annoyed because this process does not re-run myself. After I turn it off, it starts up again without knowing how t

What is Flex? What is the relationship between flex and flash? Flex is the Presentation Server (Presentation Service) released by Macromedia. It is a Java Web iner or. for an application of Net Server, the. mxmlfile (pure XML f